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A unique HMG-box domain of mouse Maelstrom binds structured RNA but not double stranded DNA.

ABSTRACT: Piwi-interacting piRNAs are a major and essential class of small RNAs in the animal germ cells with a prominent role in transposon control. Efficient piRNA biogenesis and function require a cohort of proteins conserved throughout the animal kingdom. Here we studied Maelstrom (MAEL), which is essential for piRNA biogenesis and germ cell differentiation in flies and mice. MAEL contains a high mobility group (HMG)-box domain and a Maelstrom-specific domain with a presumptive RNase H-fold. We employed a combination of sequence analyses, structural and biochemical approaches to evaluate and compare nucleic acid binding of mouse MAEL HMG-box to that of canonical HMG-box domain proteins (SRY and HMGB1a). MAEL HMG-box failed to bind double-stranded (ds)DNA but bound to structured RNA. We also identified important roles of a novel cluster of arginine residues in MAEL HMG-box in these interactions. Cumulatively, our results suggest that the MAEL HMG-box domain may contribute to MAEL function in selective processing of retrotransposon RNA into piRNAs. In this regard, a cellular role of MAEL HMG-box domain is reminiscent of that of HMGB1 as a sentinel of immunogenic nucleic acids in the innate immune response.

SUBMITTER: Genzor P

PROVIDER: S-EPMC4373776 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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A unique HMG-box domain of mouse Maelstrom binds structured RNA but not double stranded DNA.

Genzor Pavol P Bortvin Alex A

PloS one 20150325 3

Piwi-interacting piRNAs are a major and essential class of small RNAs in the animal germ cells with a prominent role in transposon control. Efficient piRNA biogenesis and function require a cohort of proteins conserved throughout the animal kingdom. Here we studied Maelstrom (MAEL), which is essential for piRNA biogenesis and germ cell differentiation in flies and mice. MAEL contains a high mobility group (HMG)-box domain and a Maelstrom-specific domain with a presumptive RNase H-fold. We employ ...[more]

PMID: 25807393

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Project description:BackgroundRAG1 and RAG2 initiate V(D)J recombination by assembling a synaptic complex with a pair of antigen receptor gene segments through interactions with their flanking recombination signal sequence (RSS), and then introducing a DNA double-strand break at each RSS, separating it from the adjacent coding segment. While the RAG proteins are sufficient to mediate RSS binding and cleavage in vitro, these activities are stimulated by the architectural DNA binding and bending factors HMGB1 and HMGB2. Two previous studies (Bergeron et al., 2005, and Dai et al., 2005) came to different conclusions regarding whether only one of the two DNA binding domains of HMGB1 is sufficient to stimulate RAG-mediated binding and cleavage of naked DNA in vitro. Here we test whether this apparent discrepancy is attributed to the choice of divalent metal ion and the concentration of HMGB1 used in the cleavage reaction.ResultsWe show here that single HMG-box domains of HMGB1 stimulate RAG-mediated RSS cleavage in a concentration-dependent manner in the presence of Mn2+, but not Mg2+. Interestingly, the inability of a single HMG-box domain to stimulate RAG-mediated RSS cleavage in Mg2+ is overcome by the addition of partner RSS to promote synapsis. Furthermore, we show that mutant forms of HMGB1 which otherwise fail to stimulate RAG-mediated RSS cleavage in Mg2+ can be substantially rescued when Mg2+ is replaced with Mn2+.ConclusionThe conflicting data published previously in two different laboratories can be substantially explained by the choice of divalent metal ion and abundance of HMGB1 in the cleavage reaction. The observation that single HMG-box domains can promote RAG-mediated 23-RSS cleavage in Mg2+ in the presence, but not absence, of partner RSS suggests that synaptic complex assembly in vitro is associated with conformational changes that alter how the RAG and/or HMGB1 proteins bind and bend DNA in a manner that functionally replaces the role of one of the HMG-box domains in RAG-HMGB1 complexes assembled on a single RSS.

Dataset Information

A unique HMG-box domain of mouse Maelstrom binds structured RNA but not double stranded DNA.

Publications

A unique HMG-box domain of mouse Maelstrom binds structured RNA but not double stranded DNA.

Similar Datasets

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