CDK13 Mutations Drive Melanoma via Accumulation of Prematurely Terminated Transcripts

Abstract

23As CDK13 mel acts via a dominant negative mechanism and no CDK13 mel mutations are 126 observed in the Cyclin binding domain, we hypothesized that Cyclin binding is required for 127 CDK13 mel dominant negative activity. To test whether the canonical CDK13 Cyclin, 128 CCNK 18,22,23 , or the related CCNT1 are required for CDK13 mel dominant negative 129 melanomagenesis in vivo, we co-injected vectors that express melanocyte-specific CDK13 mel and 130 melanocyte-specific CRISPR of ccnK or ccnT1 in the mitfa -/-; BRAF; p53 -/zebrafish melanoma 131 model. ccnK melanocyte-specific CRISPR expedited melanoma in the presence of CDK13 W878L , 132 but not alone ( Figure S1L-M). ccnT1 melanocyte-specific CRISPR suppressed CDK13 W878L and 133 CDK13 R860Q oncogenesis but had no effect by itself ( Figure 1K-L, S1O). PCR across the 134 CRISPR cut site confirmed indels directed by the ccnT1, ccnK, and control gRNAs (Figure 135 S1N). These data indicate that CDK13 mel oncogenesis requires CCNT1 for its dominant negative 136 oncogenic activity. 137 Mutant CDK13 binds chromatin in a dominant negative manner. 138As CDK13 is localized in the nucleus 24 and CDK13 WT can phosphorylate the RNAPII 139