Details

Autor(en) / Beteiligte

• Kim, Minsik
• Kim, Hee Jung
• Son, Sang Hyeon
• Yoon, Hye Jin
• Lim, Youngbin
• Lee, Jong Woo
• Seok, Yeong-Jae
• Jin, Kyeong Sik
• Yu, Yeon Gyu
• Kim, Seong Keun
• Ryu, Sangryeol
• Lee, Hyung Ho

Titel

Noncanonical DNA-binding mode of repressor and its disassembly by antirepressor

Ist Teil von

• Proceedings of the National Academy of Sciences - PNAS, 2016-05, Vol.113 (18), p.E2480-E2488

Ort / Verlag

United States: National Academy of Sciences

Erscheinungsjahr

2016

Quelle

MEDLINE

Beschreibungen/Notizen

• DNA-binding repressors are involved in transcriptional repression in many organisms. Disabling a repressor is a crucial step in activating expression of desired genes. Thus, several mechanisms have been identified for the removal of a stably bound repressor (Rep) from the operator. Here, we describe an uncharacterized mechanism of noncanonical DNA binding and induction by a Rep from the temperate Salmonella phage SPC32H; this mechanism was revealed using the crystal structures of homotetrameric Rep (92–198) and a hetero-octameric complex between the Rep and its antirepressor (Ant). The canonical method of inactivating a repressor is through the competitive binding of the antirepressor to the operator-binding site of the repressor; however, these studies revealed several noncanonical features. First, Ant does not compete for the DNA-binding region of Rep. Instead, the tetrameric Ant binds to the C-terminal domains of two asymmetric Rep dimers. Simultaneously, Ant facilitates the binding of the Rep N-terminal domains to Ant, resulting in the release of two Rep dimers from the bound DNA. Second, the dimer pairs of the N-terminal DNA-binding domains originate from different dimers of a Rep tetramer (trans model). This situation is different from that of other canonical Reps, in which two N-terminal DNA-binding domains from the same dimeric unit form a dimer upon DNA binding (cis model). On the basis of these observations, we propose a noncanonical model for the reversible inactivation of a Rep by an Ant.