FinO is an RNA chaperone that facilitates sense-antisense RNA interactions

Abstract

contributed equally to this workThe protein FinO represses F-plasmid conjugative transfer by facilitating interactions between the mRNA of the major F-plasmid transcriptional activator, TraJ, and an antisense RNA, FinP. FinO is known to bind stem±loop structures in both FinP and traJ RNAs; however, the mechanism by which FinO facilitates sense±antisense pairing is poorly understood. Here we show that FinO acts as an RNA chaperone to promote strand exchange and duplexing between minimal RNA targets derived from FinP. This strongly suggests that FinO may function to destabilize internal secondary structures within FinP and traJ RNAs that would otherwise act as a kinetic trap to sense±anti-sense pairing. The energy for FinO-catalyzed basepair destabilization does not arise from ATP hydrolysis but appears to be supplied directly from FinO RNA binding free energy. An analysis of the activities of mutants that are speci®cally de®cient in strand exchange but not RNA-binding activity demonstrates that strand exchange is essential to the ability of FinO to mediate sense±antisense RNA recognition, and that this function also plays a role in repression of conjugation in vivo.

Silencing of natural transformation by an RNA chaperone and a multitarget small RNA

“…Moreover, the ProQ/FinO domain of Lpp0148 binds RocR with a higher apparent affinity than full-length Lpp0148 and yields a well-defined shifted band. This suggests a more kinetically stable and homogeneous complex and is reminiscent of FinO, whose proteolytically stable ProQ/FinO domain binds RNA significantly more tightly than the intact protein (20). Our results also indicate that the ProQ/FinO domain of Lpp0148 binds tightly to the 3′ region of RocR (SL3) but only nonspecifically to the 5′ region (SL1 and SL2) (Fig.…”

“…S4). It was proposed that the flexible N-terminal region of FinO is necessary for sense-antisense RNA pairing (20). Although RocC lacks a similar N-terminal region, it carries an extended C-terminal domain that, despite being dispensable for RocR binding and stabilization, appears required for repression of competence (Fig.…”

“…FinO facilitates the interaction between FinP and the complementary 5′ untranslated region (UTR) of the mRNA of traJ (20,21). Sense-antisense pairing prevents translation of the TraJ transcriptional activator of the plasmid tra operon and thereby inhibits plasmid conjugation.…”

N. meningitidis1681 is a member of the FinO family of RNA chaperones

“…Support for this idea comes from the finding that FinO catalyzes the exchange of RNA strands between a two-stranded mimic of a high affinity RNA hairpin and a complementary single strand. 18 The initiation of duplexing between hairpin RNAs likely involves formation of a "kissing complex" between the complementary hairpin loops of FinP and traJ RNA, 11,19 an interaction that may be stabilized by FinO. 10,18 Here we demonstrate that the N. meningitidis protein, NMB1681, previously uncharacterized, is an RNA chaperone with structural and functional similarity to FinO.…”

“…17 Interestingly, whereas the core folded domain of FinO is sufficient for high-affinity interactions with stem-loop RNAs and protection of FinP against RNaseE, RNA chaperone activity depends upon the presence of the additional flexible N-terminal region. 18 The finding that deletion of this N-terminal region abolishes F plasmid conjugation repression strongly suggests that the RNA chaperone activity of FinO is essential for its role in the regulation of plasmid conjugation in vivo.…”