Elucidation of the exon-intron structure and size of the human protein kinase C beta gene (PRKCB)

As part of a transcriptional mapping project on human chromosome 16p12, a genomic contig was constructed that spanned the alternatively spliced human protein kinase C beta gene (PRKCB). PRKCB was determined to consist of 18 exons covering approximately 375 kb, with a particularly large intron of over 150 kb between exons 2 and 3. PRKCB is nearly 19 times larger than the highly homologous Drosophila melanogaster protein kinase C gene (dPKC), which has a similar-sized open reading frame but only 13 exons. This increase in size has occurred mostly as a result of expansion of introns, with intron size in the human gene averaging 22 kb compared with 1.5 kb in dPKC. The difference in gene size correlates with the difference in genome size, with the human haploid genome being nearly 18 times larger than the 170-Mb Drosophila haploid genome.