A single nucleotide polymorphism at the splice donor site of the human MYH base excision repair genes results in reduced translation efficiency of its transcripts.
BACKGROUND
Adenine paired with 8-hydroxyguanine, a major oxidatively damaged DNA lesion, is excised by mutY homologue (MYH) base excision repair protein in human cells. Since genetic polymorphisms of DNA repair genes associated with the activities and the expression levels of their products may modulate cancer susceptibility of individuals, we investigated the effect of a single nucleotide polymorphism (SNP) in the MYH gene on the difference in the expression levels of its products.


RESULTS
An aberrant size of the beta type nuclear form transcript was detected in a lung cancer cell line, VMRC-LCD, by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. The transcript contained the intron 1 sequence, and it was due to alternative splicing resulting from IVS1+5G/C SNP. The presence of the upstream open reading frame (ORF) on the 5'-side of the native ORF in the beta type transcript from the IVS1+5C allele could reduce the translation efficiency of the transcript into the nuclear form protein. Thus, expression vectors bearing the 5'-untranslated region sequence of either the IVS1+5G or 5C allele were constructed. In vitro translation analysis, as well as Western blot and quantitative RT-PCR analyses of the H1299 lung cancer cell line transfected with these vectors, revealed that the translation efficiency of the IVS1+5C transcript into MYH protein was much lower (approximately 30) than that of the IVS1+5G transcript.


CONCLUSIONS
The SNP at the splice donor site of the MYH gene resulted in reduced translation efficiency of its transcripts. This is the fourth case of single nucleotide variations that cause alterations in translation initiation sites and translation efficiencies in human cells.
Yamaguchi
Satoru
S
Biology Division, National Cancer Center Research Institute, Tokyo, Japan.
Shinmura
Kazuya
K
Saitoh
Takayuki
T
Takenoshita
Seiichi
S
Kuwano
Hiroyuki
H
Yokota
Jun
J
D000483:Alleles; D017398:Alternative Splicing; D001483:Base Sequence; D004247:DNA; D045647:DNA Glycosylases; D005786:Gene Expression Regulation; D005822:Genetic Vectors; D006801:Humans; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000096:biosynthesis / Q000235:genetics*; D016366:Open Reading Frames; D020641:Polymorphism, Single Nucleotide; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D014162:Transfection; D014407:Tumor Cells, Cultured
D012333:RNA, Messenger; D004247:DNA; D045647:DNA Glycosylases; D009699:N-Glycosyl Hydrolases; C061738:mutY adenine glycosylase