Relocalization of telomeric Ku and SIR proteins in response to DNA strand breaks in yeast.

Telomeric TG-rich repeats and their associated proteins protect the termini of eukaryotic chromosomes from end-to-end fusions. Associated with the cap structure at yeast telomeres is a subtelomeric domain of heterochromatin, containing the silent information regulator (SIR) complex. The Ku70/80 heterodimer (yKu) is associated both with the chromosome end and with subtelomeric chromatin. Surprisingly, both yKu and the chromatin-associated Rap1 and SIR proteins are released from telomeres in a RAD9-dependent response to DNA damage. yKu is recruited rapidly to double-strand cuts, while low levels of SIR proteins are detected near cleavage sites at later time points. Consistently, yKu- or SIR-deficient strains are hypersensitive to DNA-damaging agents. The release of yKu from telomeric chromatin may allow efficient scanning of the genome for DNA strand breaks.

Phylogenetic relationships of Apodemus Kaup, 1829 (Rodentia: Muridae) species in the Eastern Mediterranean inferred from mitochondrial DNA, with emphasis on iranian species

Wood mice of the genus Apodemus are widely distributed in Eurasia, with the Eastern Mediterranean being considered as a hotspot. Indeed, numerous species have been documented in Iran, including A. witherbyi, A. hyrcanicus, A. uralensis, A. avicennicus, A. hermonensis, and A. arianus. In this study, 129 specimens were collected from different Iranian localities and two specimens from Afghanistan. The animals were identified taxonomically and their phylogenetic relationships were investigated using cytochrome b mitochondrial DNA sequences. Five species of the genus Apodemus were identified in Iran, including A. hyrcanicus, A. witherbyi, A. cf. ponticus, A. uralensis, and A. mystacinus, beside, A. pallipes from Afghanistan. This study found no evidence of A. flavicollis or A. sylvaticus in Iran, despite their occurrence in Turkey, shedding doubt on the status of A. flavicollis in Iran, Asia Minor, and the Levant. Phylogenetic analyses imply that A. witherbyi has priority over A. avicennicus, A. hermonensis, and A. iconicus. Estimation of the divergence time for these taxa suggests a separation at around 7.2 Ma for the subgenera Karstomys (including A. mystacinus and A. epimelas) and Sylvaemus (including A. flavicollis, A. sylvaticus, A. uralensis, A. pallipes, A. hyrcanicus, A. witherbyi, and A. cf. ponticus). Within the subgenus Karstomys, the divergence times for A. mystacinus and A. epimelas were between 3.0 and 6.1 Ma, and divergence times within the subgenus Sylvaemus were between 5.2 and 6.9 Ma for A. witherbyi and other species in this subgenus. It is postulated that vicariance events including the uplifting of the Zagros Mountains and Anatolian Plateau in the middle Miocene and climate oscillations during the Messinian Salinity Crisis besides formation of the Hyrcanian tertiary forests during the Neogene probably played substantial roles in the radiation and distribution of the genus Apodemus in the Eastern Mediterranean.