LSM5 (LSM5 homolog, U6 small nuclear RNA and mRNA degradation associated) is a core spliceosomal component that functions as part of the heptameric LSM2-8 complex, which binds the 3'-terminal U-tract of U6 snRNA and participates in U4/U6-U5 tri-snRNP assembly and precatalytic spliceosome formation 1. Beyond its canonical role in pre-mRNA splicing, LSM5 regulates circadian rhythm timing; mutations in LSM5 lengthen circadian periods in plants and mammals, suggesting it fine-tunes specific signaling pathways through alternative splicing regulation 2. In disease contexts, LSM5 dysregulation has significant clinical implications. LSM5 is upregulated in nasopharyngeal carcinoma tissues, correlating with poor prognosis; knockdown inhibits cell proliferation and migration 3. Similarly, in colon cancer, elevated LSM5 expression associates with poor prognosis, and its silencing suppresses proliferation while promoting apoptosis through p53, CDKN1A, and TNFRSF10B upregulation 4. LSM5 appears among candidate irinotecan resistance markers in colorectal cancer 5. Additionally, genetic variants in LSM5 (rs215702) associate with asthenozoospermia in male infertility 6, and LSM5 protein levels are downregulated in CD8+ T lymphocytes across breast cancer subtypes 7. LSM5 also serves as a diagnostic biomarker for postmenopausal osteoporosis 8, suggesting broad pathophysiological relevance.