Structural highlights
Function[A0A0H3CAV3_CAUCN] Sigma factors are initiation factors that promote the attachment of RNA polymerase to specific initiation sites and are then released. This sigma factor is the primary sigma factor during exponential growth.[SAAS:SAAS00535554] Publication Abstract from PubMedCanonical bacterial transcription activators bind to non-transcribed promoter elements to increase transcription of their target genes. Here we report crystal structures of binary complexes comprising domains of Caulobacter crescentus GcrA, a noncanonical bacterial transcription factor, that support a novel mechanism for transcription activation through the preferential binding of methylated cis-regulatory elements and the promotion of open complex formation through an interaction with region 2 of the principal sigma factor, sigma70. We present crystal structures of the C-terminal, sigma factor-interacting domain (GcrA-SID) in complex with domain 2 of sigma70 (sigma702), and the N-terminal, DNA-binding domain (GcrA-DBD) in complex with methylated double-stranded DNA (dsDNA). The structures reveal interactions essential for transcription activation and DNA recognition by GcrA. These structures, along with mutational analyses, support a mechanism of transcription activation in which GcrA associates with RNA polymerase (RNAP) prior to promoter binding through GcrA-SID, arming RNAP with a flexible GcrA-DBD. The RNAP-GcrA complex then binds and activates target promoters harboring a methylated GcrA binding site either upstream or downstream of the transcription start site. Structural insights into the unique mechanism of transcription activation by Caulobacter crescentus GcrA.,Wu X, Haakonsen DL, Sanderlin AG, Liu YJ, Shen L, Zhuang N, Laub MT, Zhang Y Nucleic Acids Res. 2018 Mar 5. pii: 4920855. doi: 10.1093/nar/gky161. PMID:29514271[1] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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