Telomeric repeat-binding factor 1 is a protein that in humans is encoded by the TERF1 gene. [5] [6]
Telomeric repeat-binding factor 1 is a protein that in humans is encoded by the TERF1 gene. [5] [6]
The human TERF1 gene is located in the chromosome 8 at 73,921,097-73,960,357 bp. Two transcripts of this gene are alternatively spliced products. [6] The TERF1 gene is also known as TRF, PIN2 (Proteinase Inhibitor 2), TRF1, t-TRF1 and h-TRF1-AS. [7]
The protein structure contains a C-terminal Myb motif, a dimerization domain (TERF homology) near its N-terminus and an acidic N-terminus.
The cellular distribution of this DNA binding protein features the nucleoplasm, chromosomes, a telomeric region, a nuclear telomere cap complex, the cytoplasm, the spindle, the nucleus and a nucleolus and a nuclear chromosome.
TERF 1 gene encodes a telomere specific protein which is a component of the telomere's shelterin nucleoprotein complex. This protein is present at telomeres throughout the cell cycle and functions as an inhibitor of telomerase, acting in cis to limit the elongation of individual chromosome ends. It is known to protect telomeres in mammals from DNA mechanisms that are used for repair purposes and at the same time regulate the activity carried out by telomerase. The telomeric repeat binding factor 1 protein is present at telomeres, where the cells aging aspect is monitored, throughout the typical cell cycle process. [7] The progressive loss of the telomeric ends of chromosomes is an important mechanism in the timing of human cellular aging. Telomeric Repeat Factor 1 (TRF1) is a protein that binds at telomere ends.
The protein has the ultimate use of functioning as an inhibitor of telomerase, a protein enzyme that assists in the elongation of chromosomes by the addition of sequences of TTAGGG to the end of the chromosomes. The protein acts as cis-regulatory elements in the process of limiting the ends of individual chromosomes from elongating as facilitated by telomerase and the TTAGGG sequences. The structure of the protein consists of a dimerization domain close to its amino terminus, a carboxyl terminal tail, which is the free carboxyl group that terminates the end of a protein chain and an acidic amino terminus, which is the free amine group that terminates the start of a protein.
The protein is also actively involved in biological processes such as those relating to drug absorption as well as the negative regulation of the maintenance of telomere through the process of semi-conservative replication, similar to that of cis. In addition, according to Kaplan and Christopher, the protein is also involved in the biological processes of positive regulation of the polymerization of the microtubule and negative control of the process of DNA replication. [8] This protein is also useful in the biological process of mitosis and the positive regulation of mitosis. It positively regulates the mitotic cell cycle. The protein encoded by the TERF 1 gene is also involved in the biological process of cell division and the negative regulation of the maintenance of telomere facilitated by the enzyme telomerase.
Other than functioning as an inhibitor of the enzyme telomerase in the process of elongation of the ends of chromosomes, the protein has other functions. These functions include the binding of the protein, facilitation in the activity of protein homodimerization, the binding of DNA and facilitation in the activity of protein heterodimerization as well as the binding of the microtubule. Additionally, the protein has a molecular function of binding telomeric DNA and the double-stranded telomeric DNA. The telomeric repeat-binding factor 1 protein is also used in the binding of chromatin and the whole activity of bending of the DNA. [7]
TERF1 protein levels correlates with telomere length in colorectal cancer. Telomeres protect the chromosome from degradation by nucleases and end-to-end fusion. The progressive loss of the telomeric ends of chromosomes is an important mechanism in the timing of human cellular aging. Telomeric Repeat Factor 1 (TRF1) is a protein that binds at telomere ends. To measure the concentrations of TRF1 and the relationships among telomere length, telomerase activity, and TRF1 levels in tumor and normal colorectal mucosa, from normal and tumoral samples of patients who underwent surgery for colorectal cancer we analyzed TRF1 protein concentration, and telomerase activity were analysed. As result high levels of TRF1 were observed in 68.7% of tumor samples, while the majority of normal samples showed negative or weak TRF1 concentrations. Among the tumor samples, telomere length was significantly associated with TRF1 protein levels. In conclusion a relationship exists between telomere length and TRF1 abundance protein in tumor samples, which means that TRF1 is an important factor in the tumor progression and maybe a diagnostic factor.
The TERF1 encoded protein has been shown to have interactions with the following; SALL1 (Sal-like1- Drosophila, a protein.), ABL (Abelson murine leukemia viral oncogene homolog, a protein), MAPRE2 (Microtubule-associated protein RP/EB, a protein), ATM (Ataxia telangiectasia mutated, a protein kinase), PINX1 (TERF1-interacting telomerase inhibitor 1), TINF2 (TERF1-interacting telomerase nuclear factor), TNKS2 (Tankyrase, an enzyme) and NME1 (nucleoside diphosphate kinase).In conclusion, as mentioned above, the telomeric repeat-binding factor 1 protein has most of its functions related to the binding of components and regulation of processes. [8]
TERF1 has been shown to interact with:
A telomere is a region of repetitive nucleotide sequences associated with specialized proteins at the ends of linear chromosomes. Telomeres are a widespread genetic feature most commonly found in eukaryotes. In most, if not all species possessing them, they protect the terminal regions of chromosomal DNA from progressive degradation and ensure the integrity of linear chromosomes by preventing DNA repair systems from mistaking the very ends of the DNA strand for a double-strand break.
Subtelomeres are segments of DNA between telomeric caps and chromatin.
Leucyl/cystinyl aminopeptidase, also known as cystinyl aminopeptidase (CAP), insulin-regulated aminopeptidase (IRAP), human placental leucine aminopeptidase (PLAP), oxytocinase, and vasopressinase, is an enzyme of the aminopeptidase group that in humans is encoded by the LNPEP gene.
Replication protein A 70 kDa DNA-binding subunit is a protein that in humans is encoded by the RPA1 gene.
Telomeric repeat-binding factor 2 is a protein that is present at telomeres throughout the cell cycle. It is also known as TERF2, TRF2, and TRBF2, and is encoded in humans by the TERF2 gene. It is a component of the shelterin nucleoprotein complex and a second negative regulator of telomere length, playing a key role in the protective activity of telomeres. It was first reported in 1997 in the lab of Titia de Lange, where a DNA sequence similar, but not identical, to TERF1 was discovered, with respect to the Myb-domain. De Lange isolated the new Myb-containing protein sequence and called it TERF2.
RNA-binding protein FUS/TLS, also known as heterogeneous nuclear ribonucleoprotein P2 is a protein that in humans is encoded by the FUS gene.
Protection of telomeres protein 1 is a protein that in humans is encoded by the POT1 gene.
Microtubule-associated protein RP/EB family member 1 is a protein that in humans is encoded by the MAPRE1 gene.
Tankyrase, also known as tankyrase 1, is an enzyme that in humans is encoded by the TNKS gene. It inhibits the binding of TERF1 to telomeric DNA. Tankyrase attracts substantial interest in cancer research through its interaction with AXIN1 and AXIN2, which are negative regulators of pro-oncogenic β-catenin signaling. Importantly, activity in the β-catenin destruction complex can be increased by tankyrase inhibitors and thus such inhibitors are a potential therapeutic option to reduce the growth of β-catenin-dependent cancers.
TERF1-interacting nuclear factor 2 is a protein that in humans is encoded by the TINF2 gene. TINF2 is a component of the shelterin protein complex found at the end of telomeres.
Adrenocortical dysplasia protein homolog is a protein that in humans is encoded by the ACD gene.
Telomeric repeat-binding factor 2-interacting protein 1 also known as repressor activator protein 1 (Rap1) is a protein that in humans is encoded by the TERF2IP gene.
PIN2/TERF1-interacting telomerase inhibitor 1, also known as PINX1, is a human gene. PINX1 is also known as PIN2 interacting protein 1. PINX1 is a telomerase inhibitor and a possible tumor suppressor.
Tankyrase-2 is an enzyme that in humans is encoded by the TNKS2 gene.
182 kDa tankyrase-1-binding protein is an enzyme that in humans is encoded by the TNKS1BP1 gene.
DNA cross-link repair 1B protein is a protein that in humans is encoded by the DCLRE1B gene.
Telomere-binding proteins function to bind telomeric DNA in various species. In particular, telomere-binding protein refers to TTAGGG repeat binding factor-1 (TERF1) and TTAGGG repeat binding factor-2 (TERF2). Telomere sequences in humans are composed of TTAGGG sequences which provide protection and replication of chromosome ends to prevent degradation. Telomere-binding proteins can generate a T-loop to protect chromosome ends. TRFs are double-stranded proteins which are known to induce bending, looping, and pairing of DNA which aids in the formation of T-loops. They directly bind to TTAGGG repeat sequence in the DNA. There are also subtelomeric regions present for regulation. However, in humans, there are six subunits forming a complex known as shelterin.
Shelterin is a protein complex known to protect telomeres in many eukaryotes from DNA repair mechanisms, as well as to regulate telomerase activity. In mammals and other vertebrates, telomeric DNA consists of repeating double-stranded 5'-TTAGGG-3' (G-strand) sequences along with the 3'-AATCCC-5' (C-strand) complement, ending with a 50-400 nucleotide 3' (G-strand) overhang. Much of the final double-stranded portion of the telomere forms a T-loop (Telomere-loop) that is invaded by the 3' (G-strand) overhang to form a small D-loop (Displacement-loop).
Titia de Lange is the Director of the Anderson Center for Cancer Research, the Leon Hess professor and the head of Laboratory Cell Biology and Genetics at Rockefeller University.
Telomeric repeat–containing RNA (TERRA) is a long non-coding RNA transcribed from telomeres - repetitive nucleotide regions found on the ends of chromosomes that function to protect DNA from deterioration or fusion with neighboring chromosomes. TERRA has been shown to be ubiquitously expressed in almost all cell types containing linear chromosomes - including humans, mice, and yeasts. While the exact function of TERRA is still an active area of research, it is generally believed to play a role in regulating telomerase activity as well as maintaining the heterochromatic state at the ends of chromosomes. TERRA interaction with other associated telomeric proteins has also been shown to help regulate telomere integrity in a length-dependent manner.
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