BIOSYNTHESIS OF U16 SNORNA IN EARLY DEVELOPMENT OF X-LAEVIS

The U16 and U18 snoRNAs are encoded in introns of the X.laevis L1 ribo somal protein gene and originate from processing of the pre-mRNA. Thes e snoRNAs are newly synthesized around gastrula stage and progressivel y accumulate during embryogenesis. We show that the basic factors part icipating in U16 biosynthesis, such as the endonuclease involved in th e cleavage reaction and the factors necessary for stabilization of mat ure snoRNA are present from very early stages. The use of anucleolate mutants has indicated that the synthesis and accumulation of U16 and U 18 snoRNAs is not affected in the absence of ongoing rRNA transcriptio n. (C) 1997 Academic Press.