PABPABPB

PABPABPB is a proposed heteromeric complex within the poly(A) binding protein (PABP) family. It is described as arising from two paralogs, designated PABP-A and PABP-B, which are expressed in various eukaryotic systems. The term PABPABPB has appeared in studies suggesting that these paralogs can form a stable dimer that binds poly(A) tails cooperatively, potentially expanding the functional repertoire of PABP proteins.

Structure and assembly: Each subunit is thought to mirror the canonical PABP architecture, containing RNA recognition motifs (RRMs) that recognize poly(A) sequences and a C-terminal PABC domain involved in protein–protein interactions. The heterodimer is hypothesized to be stabilized by interfaces within the RRMs and the PABC-containing region, creating distinct interaction surfaces compared with homodimers. The precise stoichiometry, binding kinetics, and regulatory controls of PABPABPB are still active areas of investigation.

Function and interactions: PABPABPB is hypothesized to influence mRNA metabolism by modulating poly(A) tail accessibility and by shaping interactions with translation initiation factors and deadenylases. Potential roles include coordinating poly(A) tail length sensing, promoting translation initiation through altered eIF4G engagement, or facilitating mRNA decay pathways in a context-dependent manner. Its activity may depend on developmental stage, tissue type, or cellular stress.

Discovery status and significance: Evidence for PABPABPB comes from selective proteomic and interaction studies in some model systems, but direct in vivo validation remains limited. The existence and physiological relevance of the complex are subjects of ongoing research. No specific disease associations have been established to date; however, as a putative regulator of mRNA turnover and translation, PABPABPB could have broad implications if validated.