biostudies-literatureHartford CCRHHS | NIH | National Cancer InstituteHHS | NIH | National Cancer Institute (NCI)e0028922https://www.ebi.ac.uk/biostudies/studies/S-EPMC9753727biostudies-literatureUnknown42(12)<i>PURPL</i> is a p53-induced lncRNA that suppresses basal p53 levels. Here, we investigated <i>PURPL</i> upon p53 activation in liver cancer cells, where it is expressed at significantly higher levels than other cell types. Using isoform sequencing, we discovered novel <i>PURPL</i> transcripts that have a retained intron and/or previously unannotated exons. To determine <i>PURPL</i> function upon p53 activation, we performed transcriptome sequencing (RNA-Seq) after depleting <i>PURPL</i> using CRISPR interference (CRISPRi), followed by Nutlin treatment to induce p53. Strikingly, although loss of <i>PURPL</i> in untreated cells altered the expression of only 7 genes, loss of <i>PURPL</i> resulted in altered expression of ~800 genes upon p53 activation, revealing a context-dependent function of <i>PURPL</i>. Pathway analysis suggested that <i>PURPL</i> is important for fine-tuning the expression of specific genes required for mitosis. Consistent with these results, we observed a significant decrease in the percentage of mitotic cells upon <i>PURPL</i> depletion. Collectively, these data identify novel transcripts from the <i>PURPL</i> locus and suggest that <i>PURPL</i> delicately moderates the expression of mitotic genes in the context of p53 activation to control cell cycle arrest.Molecular and cellular biologyContext-Dependent Function of Long Noncoding RNA <i>PURPL</i> in Transcriptome Regulation during p53 Activation.PMC9753727ZIA BC 011646Chari RPongor LPasterczyk KRLal AChaudhary RGorospe MGrammatikakis IShrestha RLLi XLMuys BRZhao YFromont CKumar RAladjem MIHartford CCRKhan JChen XTsitsipatis DBasrai MAfalseContext-Dependent Function of Long Noncoding RNA <i>PURPL</i> in Transcriptome Regulation during p53 Activation.<i>PURPL</i> is a p53-induced lncRNA that suppresses basal p53 levels. Here, we investigated <i>PURPL</i> upon p53 activation in liver cancer cells, where it is expressed at significantly higher levels than other cell types. Using isoform sequencing, we discovered novel <i>PURPL</i> transcripts that have a retained intron and/or previously unannotated exons. To determine <i>PURPL</i> function upon p53 activation, we performed transcriptome sequencing (RNA-Seq) after depleting <i>PURPL</i> using CRISPR interference (CRISPRi), followed by Nutlin treatment to induce p53. Strikingly, although loss of <i>PURPL</i> in untreated cells altered the expression of only 7 genes, loss of <i>PURPL</i> resulted in altered expression of ~800 genes upon p53 activation, revealing a context-dependent function of <i>PURPL</i>. Pathway analysis suggested that <i>PURPL</i> is important for fine-tuning the expression of specific genes required for mitosis. Consistent with these results, we observed a significant decrease in the percentage of mitotic cells upon <i>PURPL</i> depletion. Collectively, these data identify novel transcripts from the <i>PURPL</i> locus and suggest that <i>PURPL</i> delicately moderates the expression of mitotic genes in the context of p53 activation to control cell cycle arrest.2022-01-01T00:00:00Z2022 Dec2026-06-13T03:29:09.294Z2025-02-19T02:37:55.857ZS-EPMC97537273634212710.1128/mcb.00289-22