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Transcription termination factor TTF‐I exhibits contrahelicase activity during DNA replication
Author(s) -
Pütter Vera,
Grummt Friedrich
Publication year - 2002
Publication title -
embo reports
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.584
H-Index - 184
eISSN - 1469-3178
pISSN - 1469-221X
DOI - 10.1093/embo-reports/kvf027
Subject(s) - helicase , minichromosome maintenance , biology , genetics , rna helicase a , ter protein , dna replication , control of chromosome duplication , transcription (linguistics) , dna , microbiology and biotechnology , gene , rna , linguistics , philosophy
In mammals, sequence‐specific termination of DNA replication within the ribosomal RNA genes is catalyzed by a defined DNA–protein complex that includes transcription termination factor I (TTF‐I). Here we show that TTF‐I acts as a polar contrahelicase contrary to the intrinsic 3′→5′ helicase activity of SV40 large T antigen. The contrahelicase activity requires binding of TTF‐I to its cognate recognition site and the presence of an auxiliary GC‐rich sequence, which is able to form a specific secondary structure. Mutations in the GC‐rich sequence lead to a loss of folding into correct secondary structure and abrogate contrahelicase activity. The finding suggests that a specific interaction between the Sal box‐bound TTF‐I and the GC‐rich sequence is essential for the inhibition of T antigen helicase. Analyses of N‐terminally truncated mutants of TTF‐I showed inhibition of helicase by the same domain of TTF‐I, which is also responsible for replication fork arrest.