Steven McKnight | |
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Steven Lanier McKnight is a professor and former chair of the department of biochemistry at UT Southwestern. His research is in the area of transcriptional regulation, drug discovery, and protein condensates.
McKnight received his bachelor's degree from University of Texas in 1974 and his PhD from University of Virginia in 1977. [1] He was a Howard Hughes Medical Institute Investigator from 1988 to 1992. [2]
Steven (Steve) McKnight was born on August 27, 1949, and was raised in El Paso, Texas. His father Frank McKnight and his mother Sara Stevens McKnight had three children, Nancy, Elizabeth, and Steven. In high school, McKnight was an accomplished athlete but an indifferent student. He enrolled in college at UT Austin in the Fall of 1968, but he dropped out one year later. At his father’s suggestion, McKnight enlisted in the Army, and in 1970 he was sent to Viet Nam, where he served as a member of a tank crew. [3] Shortly after McKnight’s arrival in Viet Nam, a land mine destroyed their tank in an explosion that McKnight and his fellow crew members barely survived. One of McKnight’s more memorable experiences during that time was adopting a dog that became the crew’s unofficial mascot.
McKnight credits his military service with instilling a sense of purpose and discipline. Upon McKnight’s return to the United States, he re-entered college, initially with the goal of becoming a high school science teacher. During his time as an undergraduate, McKnight worked in the laboratory of developmental biologist Gary Freeman, who encouraged him to apply to graduate school. Following his graduation from the University of Texas in 1974, McKnight enrolled as a Ph.D. student at the University of Virginia, where he conducted research with Professor Oscar Miller, a pioneer in electron microscopy who had been the first scientist to visualize genes being transcribed into RNA. [4] For his doctoral research, McKnight analyzed DNA replication and RNA synthesis in embryos of the fruit fly Drosophila melanogaster. [5] [6] [7]
After receiving his PhD in 1977, McKnight accepted a position as a Staff Associate at the Carnegie Institution of Washington’s Department of Embryology in Baltimore, Maryland. In the 1970s and 1980s, the Department of Embryology was at the forefront of the new science of molecular genetics, and, in particular, its application to developmental biology. [8] Don Brown, the far-sighted and charismatic leader of the Department of Embryology, had assembled a remarkable cadre of young scientists united in their determination to understand how genes are regulated and their devotion to a hands-on “small science” style of laboratory research. [9]
At the Department of Embryology, McKnight pioneered the use of molecular biological methods, including linker-scanning mutagenesis, to define the regulatory DNA sequences that comprised the promoter of the herpes simplex virus (HSV) thymidine kinase gene, the first such analysis of a eukaryotic protein-coding gene. [10] [During this time, his mentor Dr. Brown, who was famously frugal, noted that McKnight was spending an inordinate amount of money on highly purified acrylamide for gel electrophoresis, and Brown wondered whether McKnight might consider purchasing lower grade and less costly acrylamide. In response, McKnight purchased a large supply of low grade acrylamide and purified it himself. Years later, McKnight joked that this feat may have impressed Dr. Brown as much as his work on the thymidine kinase gene.]
McKnight’s work on eukaryotic promoters led him to the purification and study of gene-specific transcription factors, with particular emphasis on the manner in which they recognize their target DNA sequences. McKnight purified and isolated cDNA coding for CCAAT/Enhancer Binding Protein (C/EBP), the founding member of a broad family of transcription factors, which includes those encoded by the Myc, Fos and Jun proto-oncogenes. [11] Based on their studies of C/EBP, McKnight and his student William Landschulz, with independent contributions from Peter Kim and Erin O’Shea at MIT, defined the “basic leucine zipper” (bZIP) mode of DNA binding as a dimeric parallel coiled-coil in which amino acids in an adjacent basic region recognize a bipartite DNA target. [12] [13] [14] [15] This mode of association and DNA binding permits a large number of hetero- or homodimers starting from a much smaller number of bZIP proteins. This general strategy of combinatorial diversity has since been recognized in other families of transcription factors, such as the basic-helix-loop-helix (bHLH) family. The human genome codes for more than 40 bZIP proteins. [16]
In the late 1990s, McKnight identified the transcription factor hypoxia inducible factor 2alpha (HIF2alpha, a member of the bHLH family) and the prolyl hydroxylase enzyme that oxygenates it under normoxic conditions, thereby leading to its degradation. [17] [18] This discovery, together with the growing appreciation that some cancers grow under hypoxic stress, led McKnight to screen for and identify small-molecule inhibitors of HIF2alpha and then to found Peloton Therapeutics, a biotechnology company focused on HIF2alpha inhibitors. Peloton Therapeutics was acquired by Merck in 2019, [19] and its HIF2alpha inhibitor belzutifan was approved for therapy of renal cancer by the Food and Drug Administration (FDA) in 2023. [20]
In the late 1980’s, McKnight’s group at Carnegie and the research group of Mark Ptashne at Harvard University independently conducted functional dissections of the HSV VP16 transcription factor (McKnight) and the yeast Gal4 transcription factor (Ptashne). Both groups discovered acidic regions capable of activating transcription in the apparent absence of conventional protein structure. [21] [22] [23] The VP16 and Gal4 activation domains represented the first examples of unstructured protein domains of low sequence complexity having defined biological function. These related discoveries initiated McKnight’s quest to understand the physical biochemistry of protein domains of low sequence complexity that are now recognized to comprise ~25% of eukaryotic proteomes and to function broadly in eukaryotic cells. [24]
Independent studies performed by McKnight at UTSW and Dirk Gorlich at the Max Planck Institute for Multidisciplinary Studies in Gottingen, Germany laid the groundwork for the mechanistic dissection of the phenomenon of biological phase separation resulting from the self-association of protein domains of low sequence complexity. [25] [26] [27] [28] McKnight’s subsequent work on biological phase separation by protein domains of low sequence complexity revealed formation of weakly adhered structures as described decades earlier by Linus Pauling (reviewed in Kato and McKnight, 2017 [29] ). The weak cross-beta structures at the heart of protein phase separation are mediated by hydrogen bonding between polypeptide backbone N-H and carbonyl oxygen groups. Experimental evidence for these interactions was obtained by the use of synthetic peptides in which individual N-H groups were systematically methylated, a unique example of protein backbone “mutagenesis.” Using intein chemistry and native chemical ligation, McKnight’s team stitched synthetic peptides into the native protein sequence to systematically evaluate the importance of individual peptide N-H groups and thereby define the precise boundaries of the sequence that mediates self-association of TAR DNA-binding protein (TDP)-43. [30] [31] Subtle mutations within the low complexity domain of TDP-43 enhance its self-association in a subset of patients with amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), thereby leading to the formation of protein aggregates in neurons of affected individuals.
In 1995, after three years as Director of Research at Tularik, Inc., a San Francisco-based biotechnology company, McKnight moved to UTSW, serving as chair of the Department of Biochemistry from 1996 to 2016. Beyond UTSW, McKnight’s service to the scientific community has included serving on the Scientific Advisory Board of the Howard Hughes Medical Institute and the Institute of Molecular Pathology (Vienna, Austria), on the Board of Trustees of the Carnegie Institution of Washington, and as President of the American Society of Biochemistry and Molecular Biology. [32] At UTSW, McKnight created a set of prizes in honor of his parents, the Sara and Frank McKnight Undergraduate Prizes in Molecular Sciences. These prizes recognize college students from across the United States who have conducted outstanding research in chemistry, biological chemistry, biophysics, or quantitative biology. [33] McKnight also established the Sara and Frank McKnight Fellowships, an endowed fund that supports research conducted by young scientists within the Department of Biochemistry at UTSW. [34]
In essays and lectures, McKnight has extolled the importance of creative and curiosity-driven scientific research and of pursuing scientific directions that are off the beaten path. In a 2009 commentary, “Unconventional Wisdom” [35] McKnight offered advice and encouragement for young scientists, as well as for older scientists who are young at heart.
As president of the American Society for Biochemistry and Molecular Biology, McKnight published messages in the society's newsletter critical of young scientists, calling them "riff-raff" and saying that "The average scientist today is not of the quality of our predecessors”. [36] He complains that biomedical research now attracts researchers who “never would have survived as scientists in the 1960s and 1970s", and that the funding crisis can be attributed to the NIH review committees being “undoubtedly contaminated by riff-raff”. [37] The month prior, he had derided young scientists for being uninformed on the historic methods of biochemistry. [38] These opinions attracted media attention and criticism from many in the scientific community. [37] Future of Research, an advocacy group led by Jessica Polka that supports junior researchers satirized McKnight's comments by selling "Riff-raff" T-shirts, using the proceeds to fund the 2015 Future of Research conference. [39]
Richard Axel is an American molecular biologist and university professor in the Department of Neuroscience at Columbia University and investigator at the Howard Hughes Medical Institute. His work on the olfactory system won him and Linda Buck, a former postdoctoral research scientist in his group, the Nobel Prize in Physiology or Medicine in 2004.
Robert G. Roeder is an American biochemist. He is known as a pioneer scientist in eukaryotic transcription. He discovered three distinct nuclear RNA polymerases in 1969 and characterized many proteins involved in the regulation of transcription, including basic transcription factors and the first mammalian gene-specific activator over five decades of research. He is the recipient of the Gairdner Foundation International Award in 2000, the Albert Lasker Award for Basic Medical Research in 2003, and the Kyoto Prize in 2021. He currently serves as Arnold and Mabel Beckman Professor and Head of the Laboratory of Biochemical and Molecular Biology at The Rockefeller University.
Michael Stuart Brown ForMemRS NAS AAA&S APS is an American geneticist and Nobel laureate. He was awarded the Nobel Prize in Physiology or Medicine with Joseph L. Goldstein in 1985 for describing the regulation of cholesterol metabolism.
A leucine zipper is a common three-dimensional structural motif in proteins. They were first described by Landschulz and collaborators in 1988 when they found that an enhancer binding protein had a very characteristic 30-amino acid segment and the display of these amino acid sequences on an idealized alpha helix revealed a periodic repetition of leucine residues at every seventh position over a distance covering eight helical turns. The polypeptide segments containing these periodic arrays of leucine residues were proposed to exist in an alpha-helical conformation and the leucine side chains from one alpha helix interdigitate with those from the alpha helix of a second polypeptide, facilitating dimerization.
Kim Ashley Nasmyth is an English geneticist, the Whitley Professor of Biochemistry at the University of Oxford, a Fellow of Trinity College, Oxford, former scientific director of the Research Institute of Molecular Pathology (IMP), and former head of the Department of Biochemistry, University of Oxford. He is best known for his work on the segregation of chromosomes during cell division.
Transcription factor Sp1, also known as specificity protein 1* is a protein that in humans is encoded by the SP1 gene.
Gene structure is the organisation of specialised sequence elements within a gene. Genes contain most of the information necessary for living cells to survive and reproduce. In most organisms, genes are made of DNA, where the particular DNA sequence determines the function of the gene. A gene is transcribed (copied) from DNA into RNA, which can either be non-coding (ncRNA) with a direct function, or an intermediate messenger (mRNA) that is then translated into protein. Each of these steps is controlled by specific sequence elements, or regions, within the gene. Every gene, therefore, requires multiple sequence elements to be functional. This includes the sequence that actually encodes the functional protein or ncRNA, as well as multiple regulatory sequence regions. These regions may be as short as a few base pairs, up to many thousands of base pairs long.
Aled Morgan Edwards is the founder and Chief Executive of the Structural Genomics Consortium, a charitable public-private partnership. He is Professor of Medical Genetics and Medical Biophysics at the University of Toronto, Visiting Professor of Chemical Biology at the University of Oxford, and adjunct professor at McGill University.
Roger David Kornberg is an American biochemist and professor of structural biology at Stanford University School of Medicine. Kornberg was awarded the Nobel Prize in Chemistry in 2006 for his studies of the process by which genetic information from DNA is copied to RNA, "the molecular basis of eukaryotic transcription."
An E-box is a DNA response element found in some eukaryotes that acts as a protein-binding site and has been found to regulate gene expression in neurons, muscles, and other tissues. Its specific DNA sequence, CANNTG, with a palindromic canonical sequence of CACGTG, is recognized and bound by transcription factors to initiate gene transcription. Once the transcription factors bind to the promoters through the E-box, other enzymes can bind to the promoter and facilitate transcription from DNA to mRNA.
In molecular genetics, an untranslated region refers to either of two sections, one on each side of a coding sequence on a strand of mRNA. If it is found on the 5' side, it is called the 5' UTR, or if it is found on the 3' side, it is called the 3' UTR. mRNA is RNA that carries information from DNA to the ribosome, the site of protein synthesis (translation) within a cell. The mRNA is initially transcribed from the corresponding DNA sequence and then translated into protein. However, several regions of the mRNA are usually not translated into protein, including the 5' and 3' UTRs.
Rev-Erb alpha (Rev-Erbɑ), also known as nuclear receptor subfamily 1 group D member 1 (NR1D1), is one of two Rev-Erb proteins in the nuclear receptor (NR) family of intracellular transcription factors. In humans, REV-ERBɑ is encoded by the NR1D1 gene, which is highly conserved across animal species.
Retinoid X receptor beta (RXR-beta), also known as NR2B2 is a nuclear receptor that in humans is encoded by the RXRB gene.
RE1-Silencing Transcription factor (REST), also known as Neuron-Restrictive Silencer Factor (NRSF), is a protein which in humans is encoded by the REST gene, and acts as a transcriptional repressor. REST is expressly involved in the repression of neural genes in non-neuronal cells. Many genetic disorders have been tied to alterations in the REST expression pattern, including colon and small-cell lung carcinomas found with truncated versions of REST. In addition to these cancers, defects in REST have also been attributed a role in Huntington Disease, neuroblastomas, and the effects of epileptic seizures and ischemia.
MAD protein is a protein that in humans is encoded by the MXD1 gene.
Virginia Zakian is the Harry C. Wiess Professor in the Life Sciences in the Department of Molecular Biology at Princeton University. She is the director of the Zakian Lab, which has done important research in topics such as telomere-binding protein, telomere recombination, and telomere position effects, at Princeton University. She is a fellow at the American Academy of Microbiology and the American Association for the Advancement of Science., and is an elected member of the National Academy of Sciences (2018). Zakian served as the chair of "Princeton's Task force on the Status of Women Faculty in the Natural Sciences and Engineering at Princeton" from 2001-2003, in 2003 Zakian became Princeton University's representative to Nine Universities, Gender Equity Analysis She was elected as a member of the American Academy of Arts and Sciences in 2019.
Roger Brent is an American biologist known for his work on gene regulation and systems biology. He studies the quantitative behaviors of cell signaling systems and the origins and consequences of variation in them. He is Full Member in the Division of Basic Sciences at the Fred Hutchinson Cancer Research Center and an Affiliate Professor of Genome Sciences at the University of Washington.
Sir Hugh Reginald Brentnall Pelham, is a cell biologist who has contributed to our understanding of the body's response to rises in temperature through the synthesis of heat shock proteins. He served as director of the Medical Research Council (MRC) Laboratory of Molecular Biology (LMB) between 2006 and 2018.
The transactivation domain or trans-activating domain (TAD) is a transcription factor scaffold domain which contains binding sites for other proteins such as transcription coregulators. These binding sites are frequently referred to as activation functions (AFs). TADs are named after their amino acid composition. These amino acids are either essential for the activity or simply the most abundant in the TAD. Transactivation by the Gal4 transcription factor is mediated by acidic amino acids, whereas hydrophobic residues in Gcn4 play a similar role. Hence, the TADs in Gal4 and Gcn4 are referred to as acidic or hydrophobic, respectively.
Robert E. Kingston is an American biochemist and geneticist who studies the functional and regulatory role nucleosomes play in gene expression, specifically during early development. After receiving his PhD (1981) and completing post-doctoral research, Kingston became an assistant professor at Massachusetts General Hospital (1985), where he started a research laboratory focused on understanding chromatin's structure with regards to transcriptional regulation. As a Harvard graduate himself, Kingston has served his alma mater through his leadership.