A mutation in NPS1/STH1, an essential gene encoding a component of a novel chromatin-remodeling complex RSC, alters the chromatin structure of Saccharomyces cerevisiae centromeres

Abstract

The NPS1/STH1 gene encodes a nuclear protein essential for the progression of G2/M phase in Saccharomyces cerevisiae . Nps1p shares homology to Snf2/Swi2p, a subunit of a protein complex known as the SNF/SWI complex. Recently, Nps1p was found to be a component of a protein complex termed RSC (3) essential for mitotic growth, whereas its function is unknown. We isolated a temperature-sensitive mutant allele of NPS1 , nps1-105, and found that the mutation increases the sensitivity to thiabendazole (TBZ). At the restrictive temperature, nps1-105 arrested at the G2/M phase in MAD1-dependent manner and missegregated the mini-chromosome with higher frequency than the wild type cells. The nuclease digestion of the chromatin of the mutant cells revealed that the mutation causes the alteration of the chromatin structure around centromeres at the restrictive temperature. The results suggested that, in the nps1-105 mutant, impaired chromatin structure surrounding centromeres may lead to an impairment of kinetochore function and the cells arrest at G2/M phase through the spindle-assembly checkpoint system.

Genome-wide location and regulated recruitment of the RSC nucleosome-remodeling complex

“…RSC mutants arrest at the G 2 /M stage of the cell cycle (Cao et al 1997;Tsuchiya et al 1998;Angus-Hill et al 2001), but there is no significant overlap between RSC targets and genes involved in cell cycle control or the genes whose expression oscillates during the cell cycle. The few cell cycle-regulated genes that are bound by RSC are not biased toward any specific phase of the cell cycle.…”

“…Mutations in several RSC subunits show a typical G 2 /M arrest characterized by large budded cells containing 2N or 4N chromosomes (Cao et al 1997;Tsuchiya et al 1998;Angus-Hill et al 2001). The basis for this G 2 /M arrest is unknown, but it depends on the spindle body checkpoint.…”

Nps1/Sth1p, a component of an essential chromatin‐remodeling complex of Saccharomyces cerevisiae, is required for the maximal expression of early meiotic genes

“…Our recent analysis of the function of Nps1p in the cell division cycle, using a temperature sensitive nps1-105 mutant, showed that this mutation causes an alteration in chromatin structure surrounding centromeres at 38 ЊC and leads to G2/M arrest, possibly through the spindle-assembly checkpoint control system (Tsuchiya et al 1998). In contrast to the mitotic cell division cycle, the nps1-105 mutation affected the expression of several early meiotic genes during the sporulation process.…”

“…We have isolated a temperature-sensitive (ts) mutant allele of NPS1, nps1-105, which carries a single base substitution within the open reading frame (ORF), G to A at position 2288, resulting in the amino acid substitution of cysteine to tyrosine at position 763 (Tsuchiya et al 1998). We verified that this mutant stopped growth at 38 ЊC with an accumulation of largebudded cells containing single nuclei of a 2C-DNA content.…”

“…WWH-1D (nps1-105/NPS1), WTH-1D (nps1-105/nps1-105) and WET-1D (nps1⌬::HIS3/ nps1⌬::HIS3 pOS31pGAL1::NPS1) were as described (Tsuchiya et al 1998). WETN-1D(nps1⌬::HIS3/NPS1 pOS31pGAL1:: NPS1) was constructed by a cross between WET-1A (nps1⌬:: HIS3 pOS31pGAL1::NPS1) and W303-1B (␣).…”