Myosin-like proteins 1 and 2 are not required for silencing or telomere anchoring, but act in the Tel1 pathway of telomere length control.
The positioning of chromosomal domains in interphase nuclei is thought to facilitate transcriptional repression in yeast. It has been reported that two large coiled-coil proteins of the nuclear envelope, myosin-like proteins 1 and 2, play direct roles in anchoring yeast telomeres to the nuclear periphery, thereby creating a subcompartment enriched for Sir proteins. We have created strains containing complete deletions of mlp1 and mlp2 genes, as well as the double null strain, and find no evidence for the disruption of telomere anchoring at the nuclear periphery in these cells. We also detect no disruption of telomere-associated gene silencing. We confirm, on the other hand, that mlp mutants are particularly sensitive to DNA-damaging agents, such as bleomycin. Moreover, we show that rather than having short telomeres as in yKu-deficient strains, the mlp1 mlp2 strains have extended telomeres, resembling phenotypes of mutations in rif1. Whereas the mlp1 mlp2 mutations act on a pathway of telomere length regulation different from that of yKu70, the effects of the tel1 deletion are epistatic to the mlp mutations, suggesting that the Mlp proteins restrict telomere length in wild-type cells by influencing the Rif-Tel1 pathway of telomerase regulation.
Hediger
Florence
F
Department of Molecular Biology, University of Geneva, Quai Ernest-Ansermet 30, CH-1211 4, Geneva, Switzerland.
Dubrana
Karine
K
Gasser
Susan M
SM
D001761:Bleomycin / Q000494:pharmacology; D015139:Blotting, Southern; D002467:Cell Nucleus / Q000378:metabolism; D004247:DNA; D004249:DNA Damage; D017353:Gene Deletion; D020868:Gene Silencing; D005838:Genotype; D017404:In Situ Hybridization, Fluorescence; D008856:Microscopy, Fluorescence; D008957:Models, Genetic; D009154:Mutation; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D019098:Telomerase / Q000378:metabolism; D016615:Telomere / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D013696:Temperature
C080988:MLP1 protein, S cerevisiae; C119200:MLP2 protein, S cerevisiae; D028861:Nuclear Pore Complex Proteins; D009687:Nuclear Proteins; D016601:RNA-Binding Proteins; D029701:Saccharomyces cerevisiae Proteins; D001761:Bleomycin; D004247:DNA; D019098:Telomerase