The U6:1 (snRNA:U6:96Aa) and U6:3 (snRNA:U6:96Ac) promoters (from the pCFD4 vector) regulate expression of two guide-RNA (gRNA) sequences (GTTAACACTTGACCCGCCCG and GCCCCATCAGCGAGGACAAC) targeting the second exon of Ubc7.