HnRNP L represses cryptic exons.

The fidelity of RNA splicing is regulated by a network of splicing enhancers and repressors, although the rules that govern this process are not yet fully understood. One mechanism that contributes to splicing fidelity is the repression of nonconserved cryptic exons by splicing factors that recognize dinucleotide repeats. We previously identified that TDP-43 and PTBP1/PTBP2 are capable of repressing cryptic exons utilizing UG and CU repeats, respectively. Here we demonstrate that hnRNP L ( HNRNPL ) also represses cryptic exons by utilizing exonic CA repeats, particularly near the 5'SS. We hypothesize that hnRNP L regulates CA repeat repression for both cryptic exon repression and developmental processes such as T cell differentiation.