Deletion/insertion mutation that causes biotinidase deficiency may result from the formation of a quasipalindromic structure |
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Authors: | Pomponio RJ; Narasimhan V; Reynolds TR; Buck GA; Povirk LF; Wolf B |
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Institution: | Human Genetics, Medical College of Virginia, Virginia Commonwealth University, Richmond, USA. |
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Abstract: | Biotinidase is responsible for recycling the vitamin biotin from biocytin
that is formed after the proteolytic degradation of the biotin- dependent
carboxylases. We have identified a deletion/insertion mutation within exon
D of the human biotinidase gene in a child with biotinidase deficiency. The
mutation causes a frame shift and premature termination which are predicted
to result in a truncated protein. We propose that the mutation occurred
during DNA replication by either of two mechanisms. Both mechanisms involve
formation of a quasipalindromic hairpin loop in the template and
dissociation of DNA polymerase alpha. This mutation supports the formation
of palindromic structures as a possible cause of deletions in eukaryotes,
and supports the proposal, derived from in vitro studies, that polymerase
alpha may preferentially arrest or dissociate at specific template
sequences.
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