Alternative splicing of the human Kank gene produces two types of Kank protein

The human Kank gene encodes an ankyrin repeat domain-containing protein which regulates actin polymerization. There are at least two types of Kank protein depending on cell type, likely due to differences in transcription. Here, to examine the transcriptional initiation and genomic organization of the human Kank gene, we performed 5′-RACE (rapid amplification of cDNA ends) using total RNA from normal kidney and a human kidney cancer cell line, VMRC-RCW cells. The results suggest that the human Kank gene has several alternative first exons. While mRNA from VMRC-RCW cells encoded Kank protein (referred to as Kank-S) as reported previously, mRNA from the normal kidney tissue encoded a novel type of Kank protein (referred to as Kank-L), which contained an additional N-terminal sequence 158 amino acids long. Promoter activity and the expression of the Kank variants in normal and cancer tissues were examined.