HNRNPL encodes heterogeneous nuclear ribonucleoprotein L, an RNA-binding protein that functions as a multifaceted regulator of gene expression through both transcriptional and post-transcriptional mechanisms. The protein primarily acts as a splicing factor that binds to exonic or intronic sites with preference for CA-rich elements, functioning as either an activator or repressor of exon inclusion 1. Beyond its canonical splicing role, hnRNPL demonstrates significant transcriptional regulatory capacity through chr19 association and phase separation, particularly in cancer contexts 2. In ovarian cancer, hnRNPL forms phase-separated condensates that activate PIK3CB transcription and promote glycolysis 2. The protein also facilitates epigenetic regulation by recruiting to gene promoters and modulating histone modifications, as demonstrated in breast cancer where it forms complexes with long non-coding RNAs to upregulate AGR2 transcription through increased H3K4me3 and H3K27ac levels 3. hnRNPL plays essential roles in normal B cell activation and proliferation, regulating alternative splicing of epigenetic modifiers like KDM6A and SIRT1, which affects global histone modifications 4. Clinically, hnRNPL is frequently overexpressed in various cancers and associated with metastasis and poor prognosis, making it a potential therapeutic target 12.