A CLASS OF SINGLE-STRANDED TELOMERIC DNA-BINDING PROTEINS REQUIRED FOR RAP1P LOCALIZATION IN YEAST NUCLEI

We have identified a class of proteins that bind single-stranded telom eric DNA and are required for the nuclear organization of telomeres an d/or telomere-associated proteins, Rlf6p was identified by its sequenc e similarity to Gbp1p, a single-stranded telomeric DNA-binding protein from Chlamydomonas reinhardtii, Rlf6p and Gbp1p bind yeast single-str anded G-strand telomeric DNA. Both proteins include at least two RNA r ecognition motifs, which are found in many proteins that interact with single-stranded nucleic acids. Disruption of RLF6 alters the distribu tion of repressor/activator protein 1 (Rap1p), a telomere-associated p rotein, In wild-type yeast cells, Rap1p localizes to a small number of perinuclear spots, while in rlf6 cells Rap1p appears diffuse and nucl ear, Interestingly, telomere position effect and telomere length contr ol, which require RAP1, are unaffected by rlf6 mutations, demonstratin g that Rap1p localization can be uncoupled from other Rap1p-dependent telomere functions, In addition, expression of Chlamydomonas GBP1 rest ores perinuclear, punctate Rap1p localization in rlf6 mutant cells, Th e functional complementation of a fungal gene by an algal gene suggest s that Rlf6p and Gbp1p are members of a conserved class of single-stra nded telomeric DNA-binding proteins that influence nuclear organizatio n, Furthermore, it demonstrates that, despite their unusual codon bias , C. reinhardtii genes can be efficiently translated in Saccharomyces cerevisiae cells.