Gene heterogeneity: a basis for alternative 5.8S rRNA processing

Abstract

Two bands of 5.8S rRNA were observed when the total RNA isolated from rat or mouse tissue was separated by electrophoresis on high-resolution polyacrylamide gels under denaturing conditions. The minor form, with a lower mobility, represented 15-35% of the total 5.8S rRNA, depending on the source of the tissue. Sequence analysis and the kinetics of formation showed that this minor form is elongated at the 5' end and is not a precursor. The sequence of the minor form was found to be p(C)CGAUA[CG-, five or six nucleotides longer than the major form. The minor 5.8S rRNA constituent also formed a more stable junction complex with 28S rRNA than the shorter major sequence. The rat DNA sequence that corresponds to the additional nucleotides at the 5' end of 5.8S rRNA has been reported to be -CCGTACG-[Subrahmanyam, C. S., Cassidy, B., Busch, H., & Rothblum, L. I. (1982) Nucleic Acids Res. 10, 3667-3680], a sequence which does not contain the extra adenylic acid residue at position 4 found in the minor form. This suggests that the rodent rRNA genes are heterogeneous and that the insertion of an A residue in the ribosomal precursor RNA can generate an alternate processing site.

In vivo disruption of Xenopus U3 snRNA affects ribosomal RNA processing.

“…As can be seen in Figure 4B, the amount of newly synthesized 5.8S RNA was the same in oocytes that had been injected with oligonucleotide 61-75 (lane 2) as in control oocytes that were injected with an unrelated oligonucleotide (lane 1) or not injected with any oligonucleotide (lanes 3 and 4). The doublet band seen for 5.8S RNA reflects heterogeneity of a few nucleotides at the 5' end of both 5.8S RNA and its 32S RNA precursor, as previously reported for Xenopus (Boseley et al, 1978;Ford and Mathieson, 1978), mouse (Bowman et al, 1983), rat (Smith et al, 1984), HeLa cells (Khan and Maden, 1977) and yeast (Veldman et al, 1980). does not affect the amount of newly synthesized 5.8S, 18S and 28S rRNAs relative to controls.…”

Nuclear RNase MRP is required for correct processing of pre-5.8S rRNA in Saccharomyces cerevisiae.

“…The physiological function of having two different 5.8S rRNAs is unclear, but their occurrence has been evolutionarily conserved in mammals (2,14,25). Ribosomes that contain one or the other rRNA species might translate different sets of messages selectively (e.g., heat shock mRNAs or mRNAs destined for a particular compartment such as the mitochondria).…”

Reduced expression of the mouse ribosomal protein Rpl17 alters the diversity of mature ribosomes by enhancing production of shortened 5.8S rRNA

“…3A). Although the existence of two 5.8S forms (5.8S S and 5.8S L ) in eukaryotes has been long recognized (Rubin 1974;Smith et al 1984), this result suggested that a fraction of mature 5.8S rRNA might be derived from 32S C pre-rRNA. To verify that the stop corresponding to the 5 ′ end of 5.8S C rRNA was not an artefact of primer extension, we performed northern hybridizations (Fig.…”