3kjp
Crystal Structure of hPOT1V2-GGTTAGGGTTAG
Structural highlights
FunctionPOTE1_HUMAN Component of the telomerase ribonucleoprotein (RNP) complex that is essential for the replication of chromosome termini. Is a component of the double-stranded telomeric DNA-binding TRF1 complex which is involved in the regulation of telomere length by cis-inhibition of telomerase. Also acts as a single-stranded telomeric DNA-binding protein and thus may act as a downstream effector of the TRF1 complex and may transduce information about telomere maintenance and/or length to the telomere terminus. Component of the shelterin complex (telosome) that is involved in the regulation of telomere length and protection. Shelterin associates with arrays of double-stranded TTAGGG repeats added by telomerase and protects chromosome ends; without its protective activity, telomeres are no longer hidden from the DNA damage surveillance and chromosome ends are inappropriately processed by DNA repair pathways. Binds to two or more telomeric single-stranded 5'-TTAGGG-3' repeats (G-strand) and with high specificity to a minimal telomeric single-stranded 5'-TAGGGTTAG-3' sequence. Binds telomeric single-stranded sequences internally or at proximity of a 3'-end. Its activity is TERT dependent but it does not increase TERT activity by itself. In contrast, the ACD-POT1 heterodimer enhances telomere elongation by increasing telomerase processivity.[1] [2] [3] [4] [5] Evolutionary Conservation Check, as determined by ConSurfDB. You may read the explanation of the method and the full data available from ConSurf. Publication Abstract from PubMedThe POT1-TPP1 heterodimer, the major telomere-specific single-stranded DNA-binding protein in mammalian cells, protects chromosome ends and contributes to the regulation of telomerase. The recent discovery of telomeric RNA raises the question of how POT1 faithfully binds telomeric ssDNA and avoids illicit RNA binding that could result in its depletion from telomeres. Here we show through binding studies that a single deoxythymidine in a telomeric repeat dictates the DNA versus RNA discrimination by human POT1 and mouse POT1A. We solve the crystal structure of hPOT1 bound to DNA with a ribouridine in lieu of the critical deoxythymidine and show that this substitution results in burying the 2(')-hydroxyl group in a hydrophobic region (Phe62) of POT1 in addition to eliminating favorable hydrogen-bonding interactions at the POT1-nucleic acid interface. At amino acid 62, Phe discriminates against RNA binding and Tyr allows RNA binding. We further show that TPP1 greatly augments POT1's discrimination against RNA. How telomeric protein POT1 avoids RNA to achieve specificity for single-stranded DNA.,Nandakumar J, Podell ER, Cech TR Proc Natl Acad Sci U S A. 2010 Jan 12;107(2):651-656. Epub 2009 Dec 22. PMID:20080730[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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