Sequence and expression of a mouse U7 snRNA type II pseudogene. The U7 snRNP functions in the 3'' processing of histone pre-mRNAs of the replication variant class. The U7 snRNA is apparently the only RNA component of this minor snRNP particle. So far, the only U7 snRNA genes that have been isolated are a cluster of 5 from sea urchin. The function of the sea urchin U7 snRNP has been examined by microinjection experiments using Xenopus oocytes and the expression of these sea urchin U7 snRNA genes has been analysed by microinjection into sea urchin eggs. In our studies of U7 snRNA genes in mouse, we have isolated one of only 3 detectable U7 snRNA pseudogenes in the mouse genome and have determined its nucleotide sequence. Sequence comparisons and transcription analysis following microinjection of the gene into Xenopus oocytes supports our assignment of this isolate as a U7 snRNA type II pseudogene.