Transcriptional elongation via RNA polymerase II (Pol II) is an essential component of gene expression. It has long been thought that a necessary step of elongation is the serine 2 phosphorylation (Ser2-P) of Pol II, which is catalysed by a CDK-9/cyclin T complex called P-TEFb. Although this dogma holds true in the soma, Elizabeth Bowman, William Kelly and colleagues now present evidence (see ) that Ser2-P of Pol II in the C. elegans germline occurs via a P-TEFb-independent mechanism primarily involving CDK-12, not CDK-9, activity. Nonetheless, CDK-9 is required for C. elegans germline development, raising the possibility of an alternative essential function for CDK-9. Conversely, loss of CDK-12 and subsequent Ser2-P had little effect on germline development, suggesting a possible alternative mechanism for regulation of Pol II transcriptional elongation in the germline. These data demonstrate that Ser2-P can occur independently of P-TEFb in at least one context, and further suggest that alternative mechanisms of Pol II elongation activity might be important in establishing and/or maintaining the germline-soma distinction.
