RIM4 encodes a meiotic activator required for early events of meiosis in Saccharomyces cerevisiae.

RIM4 was previously found to be required for both the IME1- and IME2-dependent pathways of meiotic gene expression in Saccharomyces cerevisiae. We now demonstrate that RIM4 is also required for meiotic division and recombination. Furthermore, rim4Delta mutants show defects in premeiotic DNA synthesis, which can be suppressed by deletion of the SIC1 gene, which encodes a Cdk inhibitor. Expression of RIM4 is induced early in meiosis, and is dependent on IME1 but not IME2. Indeed, RIM4 itself is essential for the meiotic expression of IME2. These results suggest that RIM4 is epistatic to IME2, and is required for multiple steps during sporulation. In agreement with this interpretation, overexpression of RIM4 induces low levels of sporulation in rich medium.