The periphery of nuclear speckles defines a spatially and temporally regulated compartment of long-lived intron-retained RNAs that resolves during mitosis.

Long-lived intron-retained RNAs at nuclear speckle periphery are regulated during mitosis, with 20% of transcripts involved in genome maintenance and mitosis.

• Why it matters: Understanding how RNA localization and retention are coordinated with cell-cycle progression is crucial for insights into gene regulation and genome stability, yet this connection remains poorly understood.
• What they did: The study used compartment-resolved transcriptional inhibition, deep learning, and advanced imaging techniques to identify and characterize nuclear RNAs with long-lived retained introns in human pluripotent stem cells, focusing on their spatial distribution and features.
• The result: Findings reveal that these RNAs localize to a conserved nuclear speckle-peripheral niche during interphase, undergo kinase-dependent splicing during mitosis, and are released into the cytoplasm in early G1, linking nuclear organization to temporal RNA regulation.