S-POMBE-MEI2(+) ENCODES AN RNA-BINDING PROTEIN ESSENTIAL FOR PREMEIOTIC DNA-SYNTHESIS AND MEIOSIS-I, WHICH COOPERATES WITH A NOVEL RNA SPECIES MEIRNA

The molecular controls over meiosis are poorly understood compared with those over mitosis. Here, we show that S. pombe mei2, which is essential for the initiation of premeiotic DNA synthesis, encodes an RNA-binding protein. A temperature-sensitive mei2 mutant performs premeiotic DNA synthesis but does not undergo meiotic divisions, suggesting that Mei2 is required also for meiosis I. A novel, polyadenylated RNA species (meiRNA), which suppresses this temperature-sensitive defect if overexpressed, specifically binds to Mei2 both in vivo and in vitro. Cells without meiRNA perform premeiotic DNA synthesis but cannot undergo meiosis I. Mutations that apparently block the RNA binding ability of Mei2 inhibit premeiotic DNA synthesis. Mei2 is thus likely to couple with another RNA species to promote premeiotic DNA synthesis.