Alternative splicing of hMSH2 in normal human tissues.

hMSH2 is a homolog of bacterial mutS and yeast Msh2, a member of the group of mismatch repair genes whose products bind to mismatched regions of double-stranded DNA. We analyzed expression of hMSH2 in normal human organs by the polymerase chain reaction coupled with reverse transcription and found two novel types of alternatively spliced mRNAs that were expressed in normal human organs. One lacked exon 13, and the other lacked a portion from the second nucleotide of codon 633 to the second nucleotide of codon 719. In the latter transcript, intro 12 started with TA and ended with TT (TA-TT intron) which did not meet the GT-AG rule. Both types of transcript resulted in frameshifts which generated truncated hMSH2 proteins lacking the main part of the highly conserved region. The biological significance of the alternative splicing remains to be elucidated.