SLFN13

Model summary

A cytoplasmic RNA-processing factor that binds structured RNAs via an N-terminal nucleic-acid–binding platform and uses a central nucleotide-hydrolyzing engine to remodel RNA architecture. This remodeling exposes internal sites that the enzyme cleaves, thereby driving turnover of ribosomal and transfer RNA substrates during cytoplasmic surveillance and decay pathways. Its modular assembly suggests coordinated action with RNA decay machinery to maintain RNA quality control.

Predicted Gene Ontology terms

1. 01

   I begin by dissecting the InterPro architecture and its order along the polypeptide.

   The N-terminal half is defined by IPR029684 (Schlafen family, residues 2–655), establishing membership in the Schlafen lineage. Within this region, IPR031450 (Poxin-Schlafen/Schlafen-like, N-terminal domain, residues 90–206) precedes a tandem nucleic-acid–binding module: IPR007421 (Schlafen, AlbA_2 domain, residues 208–334) embedded within IPR038461 (Schlafen, AlbA_2 domain superfamily, residues 186–326). AlbA_2 domains are classical nucleic-acid–binding folds that stabilize interactions with structured RNA or DNA. This N-terminal arrangement creates a high-affinity platform for recognizing and positioning structured RNAs.

2. 02

   Proceeding into the central region, IPR048729 (Schlafen, GTPase-like domain, residues 404–541) introduces a P-loop NTPase scaffold that primes nucleotide-dependent remodeling.

   The C-terminal half expands this remodeling capacity: IPR027417 (P-loop containing nucleoside triphosphate hydrolase superfamily, residues 572–897) overlaps with IPR018647 (Schlafen group 3-like, DNA/RNA helicase domain, residues 595–711). Together, these modules form a GTPase/helicase-like engine that uses NTP hydrolysis to unwind or restructure RNA assemblies. The ordered architecture—N-terminal RNA-binding AlbA_2 platform followed by central GTPase-like and C-terminal helicase-like cores—causally equips the protein to bind structured RNAs and then actively remodel them through nucleotide-driven conformational changes.

3. 03

   This architecture dictates molecular function.

   The AlbA_2 platform and helicase-like core jointly create an endonuclease-competent assembly: once RNAs are captured and remodeled, internal scission becomes favorable. This supports GO:0004521 RNA endonuclease activity. The coupling of RNA recognition and NTP-driven remodeling explains how the enzyme achieves site-selective cleavage of structured substrates.

4. 04

   From function to process, endonucleolytic cleavage of structured RNAs naturally feeds into RNA turnover pathways.

   The most parsimonious routes are the decay and quality-control pathways that target structured RNAs, aligning with GO:0016075 rRNA catabolic process and GO:0016078 tRNA catabolic process. The AlbA_2 domain’s preference for structured RNAs, together with the helicase-like engine, rationalizes participation in both pathways: pre-rRNA fragments during ribosome biogenesis surveillance and misprocessed or surplus tRNAs during tRNA quality control.

5. 05

   Cellular location follows from the soluble, multi-domain architecture and absence of transmembrane features.

   Such RNA-processing assemblies typically operate in the cytoplasm, consistent with GO:0005737 cytoplasm. Cytoplasmic residency allows access to translating ribosomes and tRNA pools where cleavage and downstream decay are coordinated.

6. 06

   Mechanistically, I propose the following model.

   The N-terminal Schlafen/poxin-like and AlbA_2 modules capture structured rRNA and tRNA substrates. The central GTPase-like domain and the C-terminal helicase-like core hydrolyze NTP to transiently unwind or refold RNA, exposing cleavage sites that the endonuclease activity then exploits. This assembly likely cooperates with cytoplasmic RNA decay machinery. I therefore hypothesize transient interactions with RNA endonuclease/exoribonuclease systems and RNA granule components: the cytoplasmic RNA decay apparatus (e.g., RNase II/EXOSC10 and the RNA exosome), decapping and deadenylation factors (DCP1/2 and CCR4–NOT), and RNA granule organizers (DDX6, LSM complexes). These partners would channel cleaved RNA fragments toward rapid turnover and surveillance pathways in the cytoplasm.