MicroRNAs (miRNAs) are small, noncoding RNAs that play a vital role in gene regulation for many biological processes by binding target transcripts and marking them for degradation or post-transcriptional silencing. miRNAs undergo maturation within the nucleus beginning with cleavage ofprimary miRNA (pri-miRNA) by Drosha/DGCR8 to form premature miRNA (pre-miRNA). Whether this recognition relies more heavily on sequence motifs or structural features within the pri-miRNA is unknown. Algorithms based upon these potential recognition motifs predict many more miRNA sequences within the human genome than have been observed. To investigate the type of features thattarget a sequence for miRNA processing, we conduct a library screen of miRNA sequences within HEK293T cells to obtain a global view of miRNA processing. A reporter system consisting of GFP-P2A-puromycin and a mCherry—pri-miRNA fusion library was utilized. Library sequences that are processed by Drosha/DGCR8 lead to cleavage and degradation of the mCherry transcript and a decrease influorescence. These sequences are then analyzed for sequence motifs or structural features to elucidate how miRNAs are recognized and targeted for maturation
