The effect of histone gene deletions on chromatin structure in Saccharomyces cerevisiae

As a way of studying nucleosome assembly and maintenance in Saccharomyces cerevisiae, mutants bearing deletions or duplications of the genes encoding histones H2A and H2B were analyzed. Previous genetic analysis had shown that only one of these mutants exhibited dramatic and pleiotropic phenotypes. This mutant was also the only one that contained disrupted chromatin, suggesting that the original phenotypes were attributable to alterations in chromosome structure. The chromatin disruption in the mutant, however, did not extend over the entire genome, but rather was localized to specific regions. Thus, while the arrangement of nucleosomes over the HIS4 and GAL1 genes, the telomeres, and the long terminal repeats (delta sequences) of Ty retrotransposons appeared essentially normal, nucleosomes over the CYH2 and UBI4 genes and the centromere of chromosome III were dramatically disrupted. The observation that the mutant exhibited localized chromatin disruptions implies that the assembly or maintenance of nucleosomes differs over different parts of the yeast genome.     

Interleukin-2 induction of T-cell G1 progression and c-myb expression

In studies to determine the biochemical mechanisms responsible for cell proliferation, synchronized T cells were used as a model for cellular growth control. By metabolic and morphologic criteria, it was found that activation of the T-cell antigen receptor rendered the cells responsive to interleukin-2 (IL-2), but did not move them through the cell cycle. Instead, IL-2 stimulated G1 progression to S phase, or lymphocyte "blastic transformation." During IL-2-promoted G1 progression, expression of the cellular proto-oncogene c-myb was induced transiently at six to seven times basal levels, maximal levels occurring at the midpoint of G1.     

Masking of the Aggregation Pheromone in Dendroctonus pseudotsugae Hopk

The pheromone mask released by female Dendroctonus pseudotsugae Hopk. after the male stridulates stops aggregation of beetles in flight, but not arrestment of males, in an interaction of chemically and sonically induced behavior. This masking is viewed as a mechanism for survival through the regulation of attack and as a critical part of premating behavior.