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An intron is any nucleotide sequence within a gene that is not expressed or operative in the final RNA product. The word intron is derived from the term intragenic region, i.e., a region inside a gene. The term intron refers to both the DNA sequence within a gene and the corresponding RNA sequence in RNA transcripts. The non-intron sequences that become joined by this RNA processing to form the mature RNA are called exons.
RNA splicing is a process in molecular biology where a newly-made precursor messenger RNA (pre-mRNA) transcript is transformed into a mature messenger RNA (mRNA). It works by removing all the introns and splicing back together exons. For nuclear-encoded genes, splicing occurs in the nucleus either during or immediately after transcription. For those eukaryotic genes that contain introns, splicing is usually needed to create an mRNA molecule that can be translated into protein. For many eukaryotic introns, splicing occurs in a series of reactions which are catalyzed by the spliceosome, a complex of small nuclear ribonucleoproteins (snRNPs). There exist self-splicing introns, that is, ribozymes that can catalyze their own excision from their parent RNA molecule. The process of transcription, splicing and translation is called gene expression, the central dogma of molecular biology.
Alternative splicing, or alternative RNA splicing, or differential splicing, is an alternative splicing process during gene expression that allows a single gene to code for multiple proteins. In this process, particular exons of a gene may be included within or excluded from the final, processed messenger RNA (mRNA) produced from that gene. This means the exons are joined in different combinations, leading to different (alternative) mRNA strands. Consequently, the proteins translated from alternatively spliced mRNAs usually contain differences in their amino acid sequence and, often, in their biological functions.
A spliceosome is a large ribonucleoprotein (RNP) complex found primarily within the nucleus of eukaryotic cells. The spliceosome is assembled from small nuclear RNAs (snRNA) and numerous proteins. Small nuclear RNA (snRNA) molecules bind to specific proteins to form a small nuclear ribonucleoprotein complex, which in turn combines with other snRNPs to form a large ribonucleoprotein complex called a spliceosome. The spliceosome removes introns from a transcribed pre-mRNA, a type of primary transcript. This process is generally referred to as splicing. An analogy is a film editor, who selectively cuts out irrelevant or incorrect material from the initial film and sends the cleaned-up version to the director for the final cut.
A primary transcript is the single-stranded ribonucleic acid (RNA) product synthesized by transcription of DNA, and processed to yield various mature RNA products such as mRNAs, tRNAs, and rRNAs. The primary transcripts designated to be mRNAs are modified in preparation for translation. For example, a precursor mRNA (pre-mRNA) is a type of primary transcript that becomes a messenger RNA (mRNA) after processing.
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.
Joan Elaine Argetsinger Steitz is Sterling Professor of Molecular Biophysics and Biochemistry at Yale University and Investigator at the Howard Hughes Medical Institute. She is known for her discoveries involving RNA, including ground-breaking insights into how ribosomes interact with messenger RNA by complementary base pairing and that introns are spliced by small nuclear ribonucleic proteins (snRNPs), which occur in eukaryotes. In September 2018, Steitz won the Lasker-Koshland Award for Special Achievement in Medical Science. The Lasker award is often referred to as the 'American Nobel' because 87 of the former recipients have gone on to win Nobel prizes.
Prp24 is a protein part of the pre-messenger RNA splicing process and aids the binding of U6 snRNA to U4 snRNA during the formation of spliceosomes. Found in eukaryotes from yeast to E. coli, fungi, and humans, Prp24 was initially discovered to be an important element of RNA splicing in 1989. Mutations in Prp24 were later discovered in 1991 to suppress mutations in U4 that resulted in cold-sensitive strains of yeast, indicating its involvement in the reformation of the U4/U6 duplex after the catalytic steps of splicing.
M. R. S. Rao was an Indian scientist. He was awarded the fourth-highest civilian award, the Padma Shri, for Science and Engineering in 2010. From 2003 to 2013 he was president of Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) in Bangalore, India.
Numerous key discoveries in biology have emerged from studies of RNA, including seminal work in the fields of biochemistry, genetics, microbiology, molecular biology, molecular evolution and structural biology. As of 2010, 30 scientists have been awarded Nobel Prizes for experimental work that includes studies of RNA. Specific discoveries of high biological significance are discussed in this article.
Tracy L. Johnson is the Keith and Cecilia Terasaki Presidential Endowed Chair in the Life Sciences and Professor of Molecular, Cell, and Developmental Biology at the University of California, Los Angeles (UCLA). She is also a professor of the Howard Hughes Medical Institute. In May 2020, she was named Dean of the UCLA Division of Life Sciences.
Brenda Jean Andrews is a Canadian academic, researcher and biologist specializing in systems biology and molecular genetics.
The microprocessor complex is a protein complex involved in the early stages of processing microRNA (miRNA) and RNA interference (RNAi) in animal cells. The complex is minimally composed of the ribonuclease enzyme Drosha and the dimeric RNA-binding protein DGCR8, and cleaves primary miRNA substrates to pre-miRNA in the cell nucleus. Microprocessor is also the smaller of the two multi-protein complexes that contain human Drosha.
Sandhya Srikant Visweswariah is a scientist and academic at the Indian Institute of Science, Bangalore, India. She is currently the Chairperson of the Department of Molecular Reproduction, Development and Genetics and the Co-chair of the Centre for Biosystems Science and Engineering, Indian Institute of Science. She additionally holds the position of Adjunct Professor, Faculty of Medicine and Dentistry, University of Bergen, Norway. Her research involves the investigation of the mechanism of signal transduction via cyclic nucleotides, phosphodiesterases and novel cyclases in bacteria. Most recently, she was awarded a Bill and Melinda Gates Grand Challenges Explorations Grant for her proposal entitled "A Small Animal Model of ETEC-Mediated Diarrhea".
Tapas Kumar Kundu is an Indian molecular biologist, academician and at present the Director of Central Drug Research Institute, a prestigious research institute of Council of Scientific and Industrial Research at Lucknow. He is the head of the Transcription and Disease Laboratory of Jawaharlal Nehru Centre for Advanced Scientific Research. He is known for his studies on the regulation of Gene expression and his contributions in cancer diagnostics and the development of new drug candidates for cancer and AIDS therapeutics. He is an elected fellow of the Indian Academy of Sciences, Indian National Science Academy and the National Academy of Sciences, India and a J. C. Bose National Fellow of the Department of Science and Technology. The Council of Scientific and Industrial Research, the apex agency of the Government of India for scientific research, awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology, one of the highest Indian science awards, in 2005, for his contributions to biological sciences. He is also a recipient of the National Bioscience Award for Career Development of the Department of Biotechnology.
Ram Rajasekharan is an Indian plant biologist, food technologist and a former director of the Central Food Technological Research Institute (CFTRI), a constituent laboratory of the Council of Scientific and Industrial Research. Known for his studies on plant lipid metabolism, Rajasekharan is a former professor of eminence at the Indian Institute of Science and an elected fellow of all the three major Indian science academies namely Indian Academy of Sciences, National Academy of Sciences, India and Indian National Science Academy as well as the National Academy of Agricultural Sciences. The Department of Biotechnology of the Government of India awarded him the National Bioscience Award for Career Development, one of the highest Indian science awards, for his contributions to biosciences in 2001.
Saumitra Das is an Indian microbiologist and a professor at the Department of Microbiology and Cell Biology of the Indian Institute of Science. Known for his studies in the fields of molecular virology and molecular biology, Das is an elected fellow of all the three major Indian science academies namely, the Indian Academy of Sciences, the National Academy of Sciences, India and the Indian National Science Academy. The Department of Biotechnology of the Government of India awarded him the National Bioscience Award for Career Development, one of the highest Indian science awards, for his contributions to biosciences in 2005.
Kumaravel Somasundaram is an Indian cancer biologist and a professor at the Department of Microbiology and Cell Biology of the Indian Institute of Science. Known for his studies on the therapeutics of Glioblastoma, Somasunderam is an elected fellow of all the three major Indian science academies namely, the National Academy of Sciences, India, the Indian Academy of Sciences and the Indian National Science Academy. The Department of Biotechnology of the Government of India awarded him the National Bioscience Award for Career Development, one of the highest Indian science awards, for his contributions to biosciences in 2006.
Christine Guthrie (1945-2022) was an American yeast geneticist and American Cancer Society Research Professor of Genetics at University of California San Francisco. She showed that yeast have small nuclear RNAs (snRNAs) involved in splicing pre-messenger RNA into messenger RNA in eukaryotic cells. Guthrie cloned and sequenced the genes for yeast snRNA and established the role of base pairing between the snRNAs and their target sequences at each step in the removal of an intron. She also identified proteins that formed part of the spliceosome complex with the snRNAs. Elected to the National Academy of Sciences in 1993, Guthrie edited Guide to Yeast Genetics and Molecular Biology, an influential methods series for many years.
Jyotsna Dhawan is an Indian Cell and Developmental Biologist, Emeritus Scientist at Centre for Cellular and Molecular Biology and Visiting Professor, Institute for Stem Cell Science and Regenerative Medicine (inStem). Dhawan's research has focused on adult stem cell function and skeletal muscle regeneration. Dhawan is the current (2019-2021) President of the Indian Society for Cell Biology and the Indian Society of Developmental Biologists (2017-2020). Dhawan was elected as a fellow to the Indian National Science Academy in 2019.
References
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- ↑ "Women in Science - Initiatives - Indian Academy of Sciences" (PDF). www.ias.ac.in.
- ↑ "My journey into understanding how cells and organisms are made" (PDF). www.ias.ac.in. Retrieved 25 June 2020.
- 1 2 "INSA :: Indian Fellow Detail". insaindia.res.in. Archived from the original on 5 December 2019. Retrieved 8 December 2019.
- ↑ "MCB". mcbl.iisc.ac.in. Archived from the original on 24 July 2020. Retrieved 8 December 2019.
- ↑ "Usha VijayRaghavan". www.nasonline.org.
- ↑ "Bio". www.researchgate.net. Retrieved 25 June 2020.
- ↑ "Awards - MCB" . Retrieved 16 March 2014.