Cancer-associated snaR-A noncoding RNA interacts with core splicing machinery and disrupts processing of mRNA subpopulations II

RNA polymerase III (Pol III) transcription in cancer is linked with the emergence of snaR-A (small NF90-associated RNA isoform A), a hominid-specific ncRNA shown to enhance cell proliferation, migration, and invasion. Here, we investigate snaR-A-protein interactions to delineate its role as a putative driver of cancer progression. At the molecular level, we discover that snaR-A interacts with mRNA splicing factors, including SF3B2 - a core component of the U2 small nuclear ribonucleoprotein (snRNP) - and localizes to subnuclear foci enriched for splicing factors. Ectopic snaR-A overexpression leads to increased intron retention, a hallmark of inefficient splicing, whereas depletion of endogenous snaR-A reduces intron retention in mRNA subpopulations associated with 3' intron-exon U2 snRNP residency and nuclear speckle proximity. We further show that high levels of snaR-A promotes cell migration in cells linked with increased intron retention, consistent with evidence supporting snaR-A as a negative prognostic factor in cancer. Taken together, these findings establish snaR-A as a molecular disruptor of splicing. We propose that snaR-A-related splicing disruption may phenocopy previously reported splicing defects and consequences attributed to mutations in U2 snRNP in cancer, eliciting an alternate, non-mutational pathway during tumorigenesis. Overall design: To investigate the effect of snaR-A on splicing of mRNAs, we performed snaR-A overexpression and SF3B2 overexpression in HEK293T and A549 cells and deep sequenced the samples. The experiment included three biological replicates for scramble, snaR-A, GFP, and SF3B2 overexpression. Raw mRNA signal counts were extracted.