Yeast ribosomal protein L30 binds to an asymmetric, purine-rich internal loop in its transcript to repress its own splicing and translation. The protein-bound form of the stem-internal loop-stem RNA is an example of a kink-turn RNA structural motif. Analysis of kink-turn motifs reveals that in (2 + 5) internal loops, the identities of five nucleotides are very important, while the remaining two...

The mechanisms of pre-mRNA splicing regulation are poorly understood. Here we dissect how the Saccharomyces cerevisiae ribosomal L30 protein blocks splicing of its pre-mRNA upon binding a kink-turn structure including the 5' splice site. We show that L30 binds the nascent RPL30 transcript without preventing recognition of the 5' splice site by U1 snRNP but blocking U2 snRNP association with the...

The siphon withdrawal response (SWR) of Aplysia supports several forms of learning that are under both excitatory and inhibitory control. Here we examine the role of interneuronal processing on the regulation of siphon responses, with an emphasis on the role of inhibition. We focus on the recurrent circuit formed by the excitatory interneuron L29 and the inhibitory interneuron L30, and show tha...

The functional role of inhibition in the neural network underlying the siphon withdrawal response (SWR) of Aplysia was assessed by examining a recurrent circuit comprised of identified inhibitory interneurons (L30s), and excitatory interneurons (L29s). We previously showed that activity-dependent potentiation of the L30 inhibitory synapse onto L29 can regulate the net excitatory input elicited ...

The Saccharomyces cerevisiae ribosomal protein L30 autoregulates its own expression by binding to a purine-rich internal loop in its pre-mRNA and mRNA. NMR studies of L30 and its RNA complex showed that both the internal loop of the RNA as well as a region of the protein become substantially more ordered upon binding. A crystal structure of a maltose binding protein (MBP)-L30 fusion protein wit...

The transcript of the Saccharomyces cerevisiae gene, RPL30, is subject to regulated splicing and regulated translation, due to a structure that interacts with its own product, ribosomal protein L30. We have followed the fate of the regulated RPL30 transcripts in vivo. Initially, these transcripts abortively enter the splicing pathway, forming an unusually stable association with U1 snRNP. A lar...

The helix-loop-helix structure formed in the pre-mRNA and the mRNA of L30, a ribosomal protein from the yeast Saccharomyces cerevisiae, serves as an auto-regulatory binding site for the protein to suppress the L30 synthesis upon overproduction. Using a 33-nucleotide model RNA, the structures of the L30 binding site RNA in the presence and absence of the protein were investigated using nuclear m...

We have studied membrane topology of cytochrome P-450c21 (P450c21) using the approaches of mutagenesis and protease digestion. P450c21 is located at the cytoplasm with an N-terminal hydrophobic domain integrated into microsomal membranes. When this hydrophobic domain was replaced by a secretory signal peptide, P450c21 was translocated into the lumen and lost enzymic activity. No other topogenic...

Activity-induced short-term synaptic enhancement (STE) is a common property of neurons, one that can endow neural circuits with the capacity for rapid and flexible information processing. Evidence from a variety of systems indicates that the expression of STE depends largely on the action of residual Ca2+, which enters the presynaptic terminal during activity. We have shown previously that a Ca...

BACKGROUND Anti-mitotic compounds (microtubule de-stabilizers) such as vincristine and vinblastine have been shown clinically successful in treating various cancers. However, development of drug-resistance cells limits their efficacies in clinical situations. Therefore, experiments were performed to determine possible drug resistance mechanisms related to the application of anti-mitotic cancer ...