3u4v | pdb_00003u4v
Crystal Structure of the Tetrahymena telomerase processivity factor Teb1 OB-A
Structural highlights
FunctionTEB1_TETTS Single-stranded DNA (ssDNA)-binding protein that mediates the recruitment of telomerase to telomeric DNA (PubMed:19941821, PubMed:20363756, PubMed:22143754, PubMed:25225329). Telomerase is an essential ribonucleoprotein (RNP) enzyme that copies new telomeric repeats onto chromosome ends by repetitively synthesizing the short telomere-repeat sequence 5'-TTGGGG-3' using an RNA template component TER (PubMed:19941821). Acts as a part of a replication protein A (RPA)-related subcomplex of the holoenzyme telomerase ribonucleoprotein complex: TEB1 specifically recognizes and binds telomeric ssDNA, thereby mediating the recruitment of the holoenzyme telomerase RNP complex to telomeres (PubMed:19941821, PubMed:25225329, PubMed:27895115). TEB1 is related to RPA1 subunit of the RPA complex but is specific to telomeric DNA, which is not the case of RPA1 (PubMed:25225329).[1] [2] [3] [4] [5] Publication Abstract from PubMedTelomerase copies its internal RNA template to synthesize telomeric DNA repeats. Unlike other polymerases, telomerase can retain its single-stranded product through multiple rounds of template dissociation and repositioning to accomplish repeat addition processivity (RAP). Tetrahymena telomerase holoenzyme RAP depends on a subunit, Teb1, with autonomous DNA-binding activity. Sequence homology and domain modeling suggest that Teb1 is a paralog of RPA70C, the largest subunit of the single-stranded DNA-binding factor replication protein (RPA), but unlike RPA, Teb1 binds DNA with high specificity for telomeric repeats. To understand the structural basis and significance of telomeric-repeat DNA recognition by Teb1, we solved crystal structures of three proposed Teb1 DNA-binding domains and defined amino acids of each domain that contribute to DNA interaction. Our studies indicate that two central Teb1 DNA-binding oligonucleotide/oligosaccharide-binding-fold domains, Teb1A and Teb1B, achieve high affinity and selectivity of telomeric-repeat recognition by principles similar to the telomere end-capping protein POT1 (protection of telomeres 1). An additional C-terminal Teb1 oligonucleotide/oligosaccharide-binding-fold domain, Teb1C, has features shared with the RPA70 C-terminal domain including a putative direct DNA-binding surface that is critical for high-RAP activity of reconstituted holoenzyme. The Teb1C zinc ribbon motif does not contribute to DNA binding but is nonetheless required for high-RAP activity, perhaps contributing to Teb1 physical association with the remainder of the holoenzyme. Our results suggest the biological model that high-affinity DNA binding by Teb1AB recruits holoenzyme to telomeres and subsequent Teb1C-DNA association traps product in a sliding-clamp-like manner that does not require high-affinity DNA binding for high stability of enzyme-product association. Structural basis for Tetrahymena telomerase processivity factor Teb1 binding to single-stranded telomeric-repeat DNA.,Zeng Z, Min B, Huang J, Hong K, Yang Y, Collins K, Lei M Proc Natl Acad Sci U S A. 2011 Dec 20;108(51):20357-61. Epub 2011 Dec 5. PMID:22143754[6] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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