FIG. 1.

Protein, mRNA, and genomic structures of CDK12^S and CDK12^L. (A) Protein domains of CDK12^S and CDK12^L. The amino acid sequences of rat CDK12^S and CDK12^L were analyzed by the MotifScan program. CDK12^S and CDK12^L share 1,249 amino acids of sequence. They contain a bipartite nuclear localization signal (NLS), an arginine- and serine-rich motif (RS), and a CDC2-like kinase domain (gray boxes). CDK12^S and CDK12^L display 9 (hatched box) and 235 (blank box) distinct amino acid residues, respectively, at their carboxyl termini. Peptides 1 and 2 were used to generate antisera. (B) Genomic organization of CDK12. The exons were identified by comparing the cDNA sequences with the genomic sequences. The genomic structure of CDK12 contains 14 exons and is conserved between human, mouse, and rat. (C) mRNAs of CDK12^S and CDK12^L. The CDK12^S and CDK12^L transcripts share exons 1 to 13, and the CDK12^S transcript reads through exon 13′, while the CDK12^L transcript splices exon 13 directly to exon 14. The probes used in Northern analysis are underlined. Stop codons are labeled with asterisks. The position of the polyadenylation signal is also indicated.