SnRNAs, SnRNPs, and RNA Processing

Sequence homology between potato spindle tuber viroid and U3B snRNA

“…The nucleotide sequences of PSTV, U snRNAs of Novikoff hepatoma cells, D2 snRNA and Intron I in the 16 S-23 S spacer region from tobacco chloroplasts were taken from [6], [9], [28] and [29], respectively.…”

“…[9] for U snRNAs and [lo-121 for viroids); (iii) In the synthesis (replication) of both of them an enzyme whose sensitivity to cu-amanitin corresponds to that of DNA-dependent RNA polymerase II is involved ([13,14] [6,24,25]. Circularity of viroids vs linearity of U snRNAs as well as the absence of modified bases and a cap structure in viroids vs their presence in U snRNAs are of limited value as arguments against a possible phylogenetic relationship of the two, because these differences might have arisen later in evolution.…”

“…The complete nucleotide sequence and secondary structure of some of them are known [2,4-81. Eukaryotic small nuclear RNAs (snRNAs), of a largely unknown function, are linear singlestranded RNA molecules with a hairpin-like secondary structure (cf. [9]). All of the snRNAs of the U series (Ill-U6) have been sequenced and shown to contain a cap structure at their 5 '-end and modified bases (cf.…”

“…All of the snRNAs of the U series (Ill-U6) have been sequenced and shown to contain a cap structure at their 5 '-end and modified bases (cf. [9]). They are very conserved molecular species in nature, from dinoflagellates to man (cf.…”

“…They are very conserved molecular species in nature, from dinoflagellates to man (cf. [9]). In plants no U-type snRNAs have been identified so far.…”