HNRNPA1L2

Model summary

A nucleocytoplasmic RNA-binding protein that assembles and remodels ribonucleoprotein particles to control pre-mRNA processing and fate. It uses tandem RNA-recognition modules to bind nascent transcripts and modulate spliceosome engagement, thereby shaping constitutive and alternative splicing. Its low-complexity C-terminal region promotes oligomerization and transport competence, enabling bidirectional trafficking between nucleus and cytoplasm and transient repression of mRNA translation. Through stress-responsive assembly and phase behavior, it coordinates RNA handling during nutrient and toxicant challenges and can participate in higher-order RNP condensates that couple RNA processing with broader cellular responses.

Predicted Gene Ontology terms

1. 01

   I begin with the InterPro architecture.

   The N-terminus (residues 1–91) carries IPR012677 (Nucleotide-binding alpha-beta plait domain superfamily), a structural scaffold frequently used to support RNA-recognition modules. Within this region, residues 12–92 define IPR034845 (hnRNP A1, RNA recognition motif 1), and residues 14–97 carry IPR000504 (RNA recognition motif domain), establishing a canonical RRM1 with the classical βαββαβ fold that binds single-stranded RNA. The RRM-containing block is further annotated by IPR035979 (RNA-binding domain superfamily, residues 10–100), reinforcing that this N-terminal unit is an RNA-binding core. Immediately downstream, residues 101–212 are covered by IPR035979 again (RNA-binding domain superfamily), and residues 102–197 by IPR012677, indicating that the central region continues the RRM-like architecture with an extended β-sheet platform that stabilizes RNA contacts and protein–protein interfaces. A second RRM is evident in the central-to-C-terminal region (IPR000504, residues 105–182), consistent with tandem RRM architecture that confers high-affinity, sequence-selective RNA binding and multivalent assembly with other ribonucleoproteins. The C-terminal tail (residues 255–292) bears IPR021662 (Heterogeneous nuclear ribonucleoprotein A1/A2, C-terminal), a low-complexity, glycine-rich region that drives oligomerization, phase separation, and transport interactions typical of hnRNPs.

2. 02

   This ordered layout—an N-terminal RRM1, a second RRM-like core, and a C-terminal low-complexity tail—causes two primary molecular functions.

   First, the tandem RRMs and their αβ-plait scaffolds mediate RNA binding and ribonucleoprotein assembly, which necessitates multivalent protein contacts; this supports GO:0005515 protein binding as a core activity that stabilizes higher-order RNP complexes. The C-terminal hnRNP A1/A2 domain promotes self-association and adaptor recruitment, enabling assembly and remodeling of ribonucleoprotein particles.

3. 03

   From these molecular activities, the biological processes follow.

   The tandem RRMs and their cooperative assembly with spliceosomal factors directly drive mRNA splicing and its regulation, aligning with GO:0000398 mRNA splicing, via spliceosome and GO:0000381 regulation of alternative mRNA splicing, via spliceosome. The same RNA-binding and transport-competent architecture supports nucleocytoplasmic shuttling, explaining GO:0006405 RNA export from nucleus and GO:0051170 import into nucleus. The C-terminal low-complexity region fosters reversible condensates that can modulate stress-responsive RNA handling, consistent with cellular responses to nutrient and toxicant stress: GO:0042149 cellular response to glucose starvation and GO:0071243 cellular response to arsenic-containing substance. The low-complexity tail and propensity for β-structure nucleation also rationalize GO:1990000 amyloid fibril formation, as phase-prone, glycine-rich regions can template fibrillar assemblies under specific conditions.

4. 04

   Cellular localization emerges from the same architecture and transport logic.

   The absence of transmembrane segments and the presence of nuclear RNA-processing modules place the protein in the nucleus, specifically the GO:0005654 nucleoplasm, where pre-mRNA splicing and RNP assembly occur. The shuttling capacity and cytoplasmic roles in mRNA transport and translation repression further support nucleocytoplasmic exchange, but the dominant steady-state compartment is nucleoplasm.

5. 05

   Mechanistically, the protein likely binds nascent pre-mRNAs via its tandem RRMs, recruits or competes with spliceosomal components to modulate exon choice, and escorts processed mRNPs to nuclear export pathways.

   Its C-terminal hnRNP A1/A2 domain mediates oligomerization and transport factor docking, enabling both nuclear import/export cycles and cytoplasmic sequestration of target transcripts. Under stress, the same low-complexity tail can seed higher-order assemblies that transiently repress translation and buffer RNA pools.

6. 06

   From this model, I hypothesize interactions with spliceosome-associated factors and transport adaptors.

   Likely partners include U1/U2 snRNP components and auxiliary hnRNPs that co-regulate splicing; nuclear transport receptors that mediate import/export; and cytoplasmic RNA-binding hubs that coordinate storage and repression. These assemblies collectively explain the observed coupling of splicing regulation, nucleocytoplasmic transport, stress-responsive RNA handling, and potential roles in chromatin-associated RNA transactions.