CDK7 is a kinase that is thought to play dual roles in transcription and cell-cycle regulation by phosphorylating the carboxy-terminal domain of RNA polymerase II and also phosphorylating other cyclin-dependent kinases (CDKs). In the April 16 Proceedings of the National Academy of Sciences, Wallenfang and Seydoux at the Johns Hopkins University School of Medicine describe a study of the C. elegans cdk-7 gene (Proc Natl Acad Sci USA 2002, 99:315-320). They conducted a genome-wide screen for temperature-sensitive (ts) embryonic lethal mutants affecting transcription and came up with a ts allele of cdk-7. The cdk-7ts mutants displayed defects in mRNA synthesis and RNA polymerase phosphorylation, as well as independently regulating cell-cycle progression. They also found that cdk-7 is essential in the worm for meiosis and for maintaining normal cell ploidy.