res2+, a new member of the cdc10+/SWI4 family, controls the ‘start’ of mitotic and meiotic cycles in fission yeast.

Abstract

In the fission yeast Schizosaccharomyces pombe, the cdc10+ and res1+ genes play a crucial role in the start of mitotic and meiotic cycles. They encode structurally related transcriptional complex proteins and regulate some S phase‐specific genes. Here we report the identification of a new member of this family named as res2+. res2+ has been isolated as a multicopy suppressor of a res1‐ null mutant and specifies a 73 kDa protein, which has two copies of the Swi/ankyrin motif and shares the highest sequence and structure similarity with the Res1 protein. res2+ is largely redundant in function with res1+ and is required for the initiation of mitotic and premeiotic DNA synthesis, but has an additional role in meiotic division. Unlike res1+, res2+ is highly induced during conjugation and strongly depends on cdc10+ for its activity. We conclude that the fission yeast contains two functionally overlapping parallel ‘start’ systems, Res1‐Cdc10 and Res2‐Cdc10, the former of which plays a major role in mitotic cycle whereas the latter in meiotic cycle.

Fission Yeast Ste9, a Homolog of Hct1/Cdh1 and Fizzy-related, Is a Novel Negative Regulator of Cell Cycle Progression during G1-Phase

“…ste9 Mutants Enter the M-Phase from the Pre-Start G 1 -Phase As described above, ste9 ϩ is essential for the proper regulation of cell cycle progression in the G 1 -phase. The Cdc10 protein, in combination with Res1 or Res2, functions as a transcription factor for the genes that are essential for transition from the G 1 to the S-phase (Lowndes et al, 1992;Tanaka et al, 1992;Caligiuri and Beach, 1993;Miyamoto et al, 1994). At the restrictive temperature, cdc10 ts mutants arrest in the pre-Start period of the G 1 -phase (Nurse et al, 1976;Nurse and Bissett, 1981).…”

A Role for the START Gene–specific Transcription Factor Complex in the Inactivation of Cyclin B and Cut2 Destruction

“…Cells deleted for res2 undergo a cold-sensitive cell cycle arrest in G1 and are defective in premeiotic DNA synthesis, which results in aberrant spore formation (Miyamoto et al, 1994;Zhu et al, 1994;Ayté et al, 1997;Zhu et al, 1997). This persuaded us to determine the relationship between the mcs1-77 mutation and the res2 genomic clone.…”

“…In particular, passage through START requires the function of an essential transcription factor complex called MBF, also known as DSC-1, which controls the expression of a number of genes critical for S-phase initiation (Lowndes et al, 1991(Lowndes et al, , 1992. In fission yeast, the MBF complex, which contains the Cdc10 (Lowndes et al, 1992), Res1 (Tanaka et al,1992;Caligiuri and Beach, 1993), Res2 (Miyamoto et al, 1994;Zhu et al, 1994;Ayté et al, 1997;Zhu et al, 1997), and Rep2 (Nakashima et al, 1995) proteins, binds to MluI cell cycle box elements in the promoters of a small number of periodically expressed genes, which so far include cdc18, cdc22, cdt1, cdt2, and cig2 (Caligiuri and Beach, 1993;Kelly et al, 1993;Hofmann and Beach, 1994;Obara-Ishihara and Okayama, 1994;Zhu et al, 1994). Of these, the cdc18 gene appears to be a critical target because temperature-sensitive mutations of cdc10 can be rescued by ectopic expression of cdc18 (Kelly et al, 1993).…”

Ran1 functions to control the Cdc10/Sct1 complex through Puc1.

“…Haploid cells carrying mutations in either cdclO or sctl arrest in G, and mate to form diploid cells under appropriate nutritional conditions. The Sctl and CdclO proteins share amino acid sequence similarity to the S. pombe pctl gene product and the SW14, SW16, and MBP1 family of transcriptional regulators in S. cerevisiae (Aves et al, 1985;Breeden and Nasmyth, 1987b;Andrews and Herskowitz, 1989b;Tanaka et al, 1992;Caligiuri and Beach, 1993;Koch et al, 1993;Miyamoto et al, 1994;Zhu et al, 1994). The results of both genetic and biochemical studies suggest that CdclO and Sctl function together as a heteromeric transcription complex to activate several periodically expressed genes at the GI /S-phase transition, which include cdc22, cdcl8, and cdtl (Kelley et al, 1993;Hofmann and Beach, 1994).…”