MOLECULAR-CLONING AND FUNCTIONAL-ANALYSIS OF A HUMAN CDNA-ENCODING ANESCHERICHIA-COLI ALKB HOMOLOG, A PROTEIN INVOLVED IN DNA ALKYLATION DAMAGE REPAIR

The Escherichia coli AlkB protein is involved protecting cells against mutation and cell death induced specifically by SN2-type alkylating a gents such as methyl methanesulfonate (MMS). A human cDNA encoding a p olypeptide homologous to E.coli AlkB was discovered by searching a dat abase of expressed sequence tags (ESTs) derived from high throughput c DNA sequencing. The full-length human AlkB homolog (hABH) cDNA clone c ontains a 924 bp open reading frame encoding a 34 kDa protein which is 52% similar and 23% identical to E.coli AlkB. The hABH gene, which ma ps to chromosome 14q24, was ubiquitously expressed in 16 human tissues examined. When hABH was expressed in E.coli alkB mutant cells partial rescue of the cells from MMS-induced cell death occurred. Under the c onditions used expression of hABH in skin fibroblasts was not regulate d by treatment with MMS. Our findings show that the AlkB protein is st ructurally and functionally conserved from bacteria to human, but its regulation may have diverged during evolution.