6ldm | pdb_00006ldm
Structural basis of G-quadruplex DNA recognition by the yeast telomeric protein Rap1
Structural highlights
FunctionRAP1_YEAST Essential regulatory protein in yeast whose DNA-binding sites are found at three types of chromosomal elements: promoters, silencers, and telomeres. RAP1 is also involved in the regulation of telomere structure, where its binding sites are found within the terminal poly[C(1-3)A] sequences. The opposite regulatory functions of RAP1 are not intrinsic to its binding sites but, instead, result from interactions with different factors at promoters and silencers. RAP1 associates with SIR3 and SIR4 proteins to form a DNA-binding complex that initiates the repression at the HM loci and telomeres. May also target the binding of RIF1 and RIF2 to silencers and telomeres. Forms with GCR1 a transcriptional activation complex that is required for expression of glycolytic and ribosomal gene. Publication Abstract from PubMedG-quadruplexes are four-stranded nucleic acid structures involved in multiple cellular pathways including DNA replication and telomere maintenance. Such structures are formed by G-rich DNA sequences typified by telomeric DNA repeats. Whilst there is evidence for proteins that bind and regulate G-quadruplex formation, the molecular basis for this remains poorly understood. The budding yeast telomeric protein Rap1, originally identified as a transcriptional regulator functioning by recognizing double-stranded DNA binding sites, was one of the first proteins to be discovered to also bind and promote G-quadruplex formation in vitro. Here, we present the 2.4 A resolution crystal structure of the Rap1 DNA-binding domain in complex with a G-quadruplex. Our structure not only provides a detailed insight into the structural basis for G-quadruplex recognition by a protein, but also gives a mechanistic understanding of how the same DNA-binding domain adapts to specifically recognize different DNA structures. The key observation is the DNA-recognition helix functions in a bimodal manner: In double-stranded DNA recognition one helix face makes electrostatic interactions with the major groove of DNA, whereas in G-quadruplex recognition a different helix face is used to make primarily hydrophobic interactions with the planar face of a G-tetrad. Structural basis of G-quadruplex DNA recognition by the yeast telomeric protein Rap1.,Traczyk A, Liew CW, Gill DJ, Rhodes D Nucleic Acids Res. 2020 Mar 18. pii: 5809672. doi: 10.1093/nar/gkaa171. PMID:32187364[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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