Publication Date:
2012-10-24
Description:
Extragenic sequences in genomes, such as microRNA and CRISPR, are vital players in the cell. Repetitive extragenic palindromic sequences (REPs) are a class of extragenic sequences, which form nucleotide stem-loop structures. REPs are found in many bacterial species at a high copy number and are important in regulation of certain bacterial functions, such as Integration Host Factor recruitment and mRNA turnover. Although a new clade of putative transposases (RAYTs or TnpA REP ) is often associated with an increase in these repeats, it is not clear how these proteins might have directed amplification of REPs. We report here the structure to 2.6 Å of TnpA REP from Escherichia coli MG1655 bound to a REP. Sequence analysis showed that TnpA REP is highly related to the IS 200 /IS 605 family, but in contrast to IS 200 /IS 605 transposases, TnpA REP is a monomer, is auto-inhibited and is active only in manganese. These features suggest that, relative to IS 200 /IS 605 transposases, it has evolved a different mechanism for the movement of discrete segments of DNA and has been severely down-regulated, perhaps to prevent REPs from sweeping through genomes.
Print ISSN:
0305-1048
Electronic ISSN:
1362-4962
Topics:
Biology
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