The absence of the Isw2p–Itc1p chromatin‐remodelling complex induces mating type‐specific and Flo11p‐independent invasive growth of Saccharomyces cerevisiae

Abstract

The Isw2p-Itc1p chromatin remodelling complex of Saccharomyces cerevisiae is a member of the ISWI class of ATPases with a nucleosome spacing activity, involved in regulation of expression of a broad spectrum of genes. Its absence causes derepression of a-specific genes and aberrant morphology in α-mating type cells. We report here that the deletion of the ISW2 gene in the originally non-invasive BY strain induces mating type-specific invasive growth strongly affected by nitrogen starvation. Although the Flo11 protein was postulated to be critical for haploid invasive growth, we showed that the invasive growth caused by the isw2 and itc1 deletions in α-mating type cells was Flo11p-independent. This type of invasive growth was proved to be a consequence of the activation of the pheromone response pathway. Our results suggest that Isw2 and Itc1 proteins do not have the same impact on the described phenomenon.

Deregulation of DSE1 Gene Expression Results in Aberrant Budding within the Birth Scar and Cell Wall Integrity Pathway Activation in Saccharomyces cerevisiae

“…The isw2⌬ MAT␣ cells displayed an aberrant morphology and a complex distribution of the cell wall chitin involving its accumulation at the base of the shmoolike projections (Fig. 2) as a consequence of an autocrine activation of the pheromone response pathway (31). The pattern of the cell wall labeling of the isw2⌬ MATa cells was similar to that of the wild-type cells.…”

“…Here we tested by Western blotting whether the CWI pathway was also activated in the isw2⌬ ste4⌬ MAT␣ strain, lacking indirect defects induced by an autocrine activation of the pheromone response pathway (31). As shown in Fig.…”

“…The S. cerevisiae strains used in this study are listed in Table 1 and were derived from either BY4741 and BY4742 (Euroscarf collection) or S288C (yeast green fluorescent protein [GFP] clone collection; Invitrogen). The isw2⌬::HIS3MX strain was prepared by replacing the ISW2 gene in BY4742 with the HIS3MX cassette similarly as described previously (31). Deletion strains expressing specific GFP fusions from the chromosomal locus and double deletion strains were generated by mating, subsequent sporulation on Fowel medium, and spore dissection using the Singer micromanipulator.…”

“…The Isw2 chromatin remodeling complex is involved in the transcriptional regulation of a broad spectrum of genes by influencing the accessibility of chromatin to the transcriptional machinery (32). It was found to participate, e.g., in the repression of the mitotic cyclin-encoding gene CLB2 (24) and MATa-specific genes in MAT␣ cells (20,31). The absence of either Isw2 or Itc1 in MAT␣ cells results in an inappropriate a-factor production and an autocrine activation of the pheromone response pathway.…”

“…The absence of either Isw2 or Itc1 in MAT␣ cells results in an inappropriate a-factor production and an autocrine activation of the pheromone response pathway. As a result, the pheromone-inducible genes are upregulated and cells display altered morphology resembling budding "shmoos" (20,28,30,31). However, the level of derepression of MATa-specific genes in isw2⌬ MAT␣ cells as a direct effect of the Isw2 absence is very low.…”