Accurate repair of non-cohesive, double strand breaks in Saccharomyces cerevisiae: enhancement by homology-assisted end-joining.

Although the joining of blunt ends in yeast by non-homologous end joining (NHEJ) is reported to be inefficient in comparison to cohesive-end joining (Boulton and Jackson, 1996), we find that efficiency varies greatly, depending on strain, growth phase and sequence. In particular, the levels of efficiency of recircularization of a plasmid linearized by non-cohesive cleavage is augmented to that of cohesive end joining if the cleavage cut site is flanked by sequences present in the genome. We call this enhancement 'homology-assisted end joining' (HAEJ), which depends on components of the NHEJ repair pathway and, in some cases, on components of the homologous recombination (HR) pathway and on Htl1 a component of the remodels structure of chromatin (RSC) complex.

A study of biochemical and functional interactions of Htl1p, a putative component of the Saccharomyces cerevisiae, Rsc chromatin-remodeling complex.

HTL1, a small gene of Saccharomyces cerevisiae, encodes a 78-aminoacid peptide that influences the performance of a wide range of cellular processes [Lanzuolo, C., Ederle, S., Pollice, A.

The finger subdomain of yeast telomerase cooperates with Pif1p to limit telomere elongation.

Telomere synthesis depends on telomerase, which contains an RNA subunit linked to a specialized reverse transcriptase subunit and several associated proteins. Here we report the characterization of four mutations in the yeast reverse transcriptase subunit Est2p that cause an overelongation of telomeres and an increase in the association of Est1p with telomeres during S phase. These 'up-mutations' are clustered in the finger subdomain of the reverse transcriptase.

Human telomeric position effect is determined by chromosomal context and telomeric chromatin integrity.

We investigated the influence of telomere proximity and composition on the expression of an EGFP reporter gene in human cells. In transient transfection assays, telomeric DNA does not repress EGFP but rather slightly increases its expression. In contrast, in stable cell lines, the same reporter construct is repressed when inserted at a subtelomeric location.