A survey of splice variants of the human hypoxanthine phosphoribosyl transferase and DNA polymerase beta genes: products of alternative or aberrant splicing?

Errors during the pre-mRNA splicing of metazoan genes can degrade the transmission of genetic information, and have been associated with a variety of human diseases. In order to characterize the mutagenic and pathogenic potential of mis-splicing, we have surveyed and quantified the aberrant splice variants in the human hypoxanthine phosphoribosyl transferase (HPRT) and DNA polymerase beta (POLB) in the presence and the absence of the Nonsense Mediated Decay (NMD) pathway, which removes transcripts with premature termination codons. POLB exhibits a high frequency of splice variants (40-60%), whereas the frequency of HPRT splice variants is considerably lower (approximately 1%). Treatment of cells with emetine to inactivate NMD alters both the spectrum and frequency of splice variants of POLB and HPRT. It is not certain at this point, whether POLB and HPRT splice variants are the result of regulated alternative splicing processes or the result of aberrant splicing, but it appears likely that at least some of the variants are the result of splicing errors. Several mechanisms that may contribute to aberrant splicing are discussed.