GEOapplication/xmlftp://ftp.ncbi.nlm.nih.gov/geo/series/GSE327nnn/GSE327794/primaryOK200TranscriptomicsHomo sapiensExpression profiling by high throughput sequencinghttps://www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE327794GEOGSEfalseThe periphery of nuclear speckles defines a spatially and temporally regulated compartment of long-lived intron-retained RNAs that resolves during mitosisRNA localization adds a fundamental layer to gene expression by determining when and where translation-ready mRNAs become available. Here, we identify a distinct subnuclear RNA niche at the nuclear speckle periphery that links intron retention to cell-cycle-timed RNA release. Using compartment-resolved transcriptional inhibition, sequence-based deep learning, and single-molecule and super-resolution RNA imaging in human pluripotent stem cells, we define a class of nuclear RNAs with long-lived retained introns (LL-IR-RNAs) that maintain stable intron retention for hours and are enriched in genome maintenance and mitosis regulators, including centromere and kinetochore assembly, DNA repair, and telomere maintenance. Long-lived retained introns are characterized by elevated GC content, predicted structural stability, and nuclear speckle-associated RBPs. In interphase, LL-IR-RNAs localize to a nuclear speckle-proximal niche conserved between cell types. During mitotic remodeling, they undergo coordinated, kinase-dependent splicing and populate the cytoplasm of early G1 daughter cells. These findings link cis-encoded intronic features, subnuclear organization and mitotic remodeling to temporal control of RNA fate.2026/06/24GSE327794GSM9666070GSM9666063GSM9666062GSM9666061GSM9666060GSM9666067GSM9666056GSM9666066GSM9666055GSM9666065GSM9666064GSM9666059GSM9666069GSM9666058GSM9666057GSM966606824676327794Homo sapiens