Saccharomyces cerevisiae U14 small nuclear RNA has little secondary structure and appears to be produced by post-transcriptional processing

Yeast U14 small nuclear (sn) RNA is required for normal processing of rRNA. The sequence and folding properties of U14 were analyzed in the present study, with the aim of defining the structures of natural U14 subspecies and characterizing the folding properties of free U14 RNA. Natural U14 was determined to consist of four subspecies of 125-128 nucleotides, none containing a 5'-cap structure. Length heterogeneity occurs at both ends and is presumed to reflect post-transcriptional processing of U14 precursors. Results from nuclease and chemical probing revealed that U14 has surprisingly little secondary structure overall. Three essential sequence elements conserved among all U14 RNAs occur in regions that are largely single-stranded, i.e. box C, box D, and a 13-nucleotide segment complementary to 18 S rRNA; a non-essential 14-nucleotide sequence complementary to 18 S rRNA is also unpaired. Two non-conserved segments required for activity are part of a stably folded 32-base domain that is unique to yeast U14. Finally, a 5'-, 3'-stem shown earlier to be required for U14 accumulation appears to exist only in precursors to U14 and not in protein-free mature RNA. The implications of these results are discussed in terms of U14 synthesis and function.

Accumulation of U14 small nuclear RNA in Saccharomyces cerevisiae requires box C, box D, and a 5', 3' terminal stem

U14 is one of several nucleolar small nuclear RNAs required for normal processing of rRNA. Functional mapping of U14 from Saccharomyces cerevisiae has yielded a number of mutants defective in U14 accumulation or function. In this study, we have further defined three structural elements required for U14 accumulation. The essential elements include the U14-conserved box C and box D sequences and a 5', 3' terminal stem. The box elements are coconserved among several nucleolar small nuclear RNAs and have been implicated in binding of the protein fibrillarin. New mutational results show that the first GA bases of the box C sequence UGAUGA are essential, and two vital bases in box D have also been identified. An intragenic suppressor of a lethal box C mutant has been isolated and shown to contain a new box C-like PyGAUG sequence two bases upstream of normal box C. The importance of the terminal stem was confirmed from new compensatory base changes and the finding that accumulation defects in the box elements can be complemented by extending the terminal stem. The results suggest that the observed defects in accumulation reflect U14 instability and that protein binding to one or more of these elements is required for metabolic stability.

Sacroepidural analgesia for post-operative pain relief in children

For evaluation of the practicality of epidural analgesia for alleviation of post-operative pain, 66 class I or II patients with age ranging from 6 months to 12 years undergoing elective surgical procedures below the lower abdomen were enrolled for study during the period from January to April 1989. Before termination of general anesthesia a single dose of 0.25% bupivacaine, respectively at 0.25 mL/kg (Ideal body weight), 0.5 mL/kg, 0.75 mL/kg, 1.0 mL/kg and 1.25 mL/kg was given sacroepidurally to 5 groups of patients. Our results showed that for surgery below the lower abdomen a dose at 1.0 mL/kg was sufficient to suffice the need for relief of post-operative pain. At this dosage it achieved a neural block up to T8-T6 and provided with an analgesia that could last 6.0 +/- 2.1 hours. During the entire course there were no untoward effects such as hypotension, bradycardia, vomiting and shivering to come about. Therefore, sacroepidural analgesia with 0.25% bupivacaine at fitting single dose is safe and feasible in children as far as relief of post-operative pain for procedures below the lower abdomen is concerned.