Phosphorylation-controlled nuclear speckle dynamics regulate splicing

Understanding how the spliceosome integrates regulatory cues to generate RNA diversity remains a central question in gene expression control. Emerging evidence reveals a multilayered framework in which splicing is governed by nuclear architecture and the physical state of nuclear speckles. These condensates function as phosphorylation-sensitive hubs that concentrate splicing machinery and couple signaling pathways to RNA processing. Chromatin organization, transcript architecture, and condensate properties are tightly coordinated, adding spatial constraints to spliceosome function. Recent findings further uncover temporal regulation through cell cycle and ultradian dynamics of speckle assembly. In this review, we synthesize these advances and propose a unified model in which charge-dependent phosphorylation of splicing factors drives condensate remodeling, linking nuclear organization to regulated splicing outcomes across space and time.