Morgenthaler P M, Holzhäuser D
Nestec Ltd. Research Centre, Quality and Safety Assurance Department, Lausanne, Switzerland.
Carcinogenesis. 1995 Apr;16(4):713-8. doi: 10.1093/carcin/16.4.713.
2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a heterocyclic aromatic amine that is formed in abundance in cooked meats, has been found to be mutagenic in human lymphoblastoid TK6 cells at the thymidine kinase and hypoxanthine-guanine phosphoribosyl transferase (hgprt) loci. The mutations induced at the hgprt locus have been analysed. Of the mutations that have been identified, 60% were found in the coding sequence of the gene. Forty percent were in the introns which resulted in aberrant splicing and consequently, leading to exon losses in the mature hprt mRNA. Mutations resulting in a loss of exonIII appeared most frequently followed by losses of exonVI, exonVIII and partial loss of exonIX. All identified mutations occurred at GC base pairs, consistent with the adducts of PhIP that have been found previously and suggesting that the N-(deoxyguanosin-8-yl)-2-amino-1-methyl-6-phenylimidazo[4,5- b]pyridine, (dG-C8-PhIP) adduct may be the premutagenic lesion. Most of the mutations are GC-->TA transversions except for a cluster of single base pair deletions in a run of guanines. There appears to be strand bias in the induction of mutations with 85% of the mutations on the non-transcribed strand. Although the number of mutations analysed is limited (54 mutants), there are several sites (positions 166 and 207 of the coding sequence, and the splice acceptor site of exonIII) which are overrepresented. There is a preference for a 5' purine but not a strong bias for 3' A as has been found for other mutagens that form a premutagenic lesion at G. Triplet analysis shows that the triplets, 5'GGA3' and 5'AGG3', where the middle base is mutated are preferred.
2-氨基-1-甲基-6-苯基咪唑并[4,5-b]吡啶（PhIP）是一种在熟肉中大量形成的杂环芳香胺，已发现在人淋巴母细胞TK6细胞的胸苷激酶和次黄嘌呤-鸟嘌呤磷酸核糖转移酶（hgprt）位点具有致突变性。已对hgprt位点诱导的突变进行了分析。在已鉴定的突变中，60%位于该基因的编码序列中。40%位于内含子中，导致异常剪接，进而导致成熟hprt mRNA中外显子缺失。导致外显子III缺失的突变出现频率最高，其次是外显子VI、外显子VIII缺失以及外显子IX部分缺失。所有已鉴定的突变均发生在GC碱基对处，这与先前发现的PhIP加合物一致，表明N-（脱氧鸟苷-8-基）-2-氨基-1-甲基-6-苯基咪唑并[4,5-b]吡啶（dG-C8-PhIP）加合物可能是前诱变损伤。除了一串鸟嘌呤中的单碱基对缺失簇外，大多数突变是GC→TA颠换。在突变诱导中似乎存在链偏向性，85%的突变发生在非转录链上。尽管分析的突变数量有限（54个突变体），但有几个位点（编码序列的第166和207位，以及外显子III的剪接受体位点）出现频率过高。对于5'嘌呤存在偏好，但对于3'A没有像在G处形成前诱变损伤的其他诱变剂那样强烈的偏向性。三联体分析表明，中间碱基发生突变的三联体5'GGA3'和5'AGG3'是优选的。
