Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.27.4 (ribonuclease)
 6,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It has been shown previously that maternal mRNA, synthesized and stored in growing oocytes, is stabilized and blocked from translation through various mechanisms including restricted polyadenylation and the binding of proteins to 3' regulatory elements. In addition to binding sequence-specific proteins, the bulk of stored mRNA is packaged with a set of 'masking' proteins, the most abundant of which are the phosphoproteins pp56 and pp60. In this report these proteins are shown to be bound to heterogeneous mRNA sequences and not to the 3' poly(A) tract. Crosslinking studies demonstrate that all of the pp56/60 present makes direct contact with the RNA. In vitro binding studies confirm that pp56/60 interact with single-stranded RNA of heterogeneous sequence, such as occurring in the maternal mRNA encoding cyclin B1. However, binding is equally effective to capped and polyadenylated cyclin mRNA, to truncated mRNA lacking 5' and 3' non-coding regions and even to the antisense sequence. Lengths of 70-80 nucleotides are protected from ribonuclease digestion after protein binding. Although no extended binding motif could be detected, binding does appear to have some specificity in that it is not competed out by 100-fold excess of double-stranded RNA, transfer RNA, poly(A) and various other homopolymers and heteropolymers. The sequence which competes most efficiently is the mixed polypyrimidine, poly(C,U). Crosslinking of RNA-protein complexes, followed by ribonuclease digestion, suggests that the arrangement of proteins on RNA is as dimers. Dimerization appears to be stabilized by phosphorylation of pp56/60. These results are discussed in terms of the known structures of pp56/60.
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PMID:Binding of Xenopus oocyte masking proteins to mRNA sequences. 145 24

The effects of estradiol treatment, which stimulates cell division in rat uterine epithelial cells, on the in vivo expression of heparin-binding epidermal growth factor (HB-EGF), cyclin D1, and cyclin B1 messenger RNA (mRNA) in these cells have been examined using ribonuclease protection assays. Estradiol gave rise to significant increases in steady state levels of HB-EGF 2 and 24 h after treatment. Cyclin D1 mRNA levels were elevated 8 and 10 h after estradiol administration, corresponding to the G1 phase of the mitotic cycle, and cyclin B1 mRNA was only expressed 16-24 h after estradiol treatment, which corresponds to the G2 and M phases of the rat uterine epithelial cell cycle. Estradiol-stimulated increases in HB-EGF mRNA were not affected by treatment with cycloheximide, but were inhibited by the estrogen antagonist compound, ICI 164,384, demonstrating that the estrogen-stimulated increase in HB-EGF mRNA is a primary, estrogen receptor-mediated response of rat uterine epithelium to estradiol. Progesterone treatment, which blocks epithelial cells in G1 of the cycle, suppressed levels of HB-EGF mRNA below those observed in ovariectomized rats. These results indicate that HB-EGF mediates the regulatory effects of both estradiol and progesterone on rat uterine epithelial cell proliferation through an effect on the production of G1 phase molecules such as cyclin D1.
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PMID:Mediators of estradiol-stimulated mitosis in the rat uterine luminal epithelium. 949 26