Biomedical subjects

U Guddat

Publications and source records attributed to U Guddat.

13 recordsLinked to original sources

PubMed1992

RNA and DNA binding zinc fingers in Xenopus TFIIIA.

The nine tandem zinc finger repeats in the 5S gene-specific transcription factor IIIA (TFIIIA) from Xenopus mediate specific binding to 5S DNA as well as to 5S ribosomal RNA. A comparative functional analysis of a systematic set of TFIIIA zinc finger combinations reveals that most, if not all, participate in both DNA and RNA binding. Minimal sets of fingers sufficient for DNA and RNA recognition are different. In RNA binding, most finger elements are found to be functionally equivalent. However, the nonessential finger 6 exhibits RNA binding characteristics distinct from the other eight modules. The secondary/tertiary structure of the central domain in 5S RNA, not its primary sequence, is found to carry the essential structural information for TFIIIA binding in Xenopus oocytes. Taken together, our findings suggest that RNA and DNA binding are overlapping, though separable functions of the nine zinc finger elements in TFIIIA, occurring via fundamentally different molecular mechanisms.

Animals↗

PubMed1992

Assembly and nuclear transport of the U4 and U4/U6 snRNPs.

We have analyzed the assembly of the spliceosomal U4/U6 snRNP by injecting synthetic wild-type and mutant U4 RNAs into the cytoplasm of Xenopus oocytes and determining the cytoplasmic-nuclear distribution of U4 and U4/U6 snRNPs by CsCl density gradient centrifugation. Whereas the U4 snRNP was localized in both the cytoplasmic and nuclear fractions, the U4/U6 snRNP was detected exclusively in the nuclear fraction. Cytoplasmic-nuclear migration of the U4 snRNP did not depend on the stem II nor on the 5' stem-loop region of U4 RNA. Our data provide strong evidence that, following the cytoplasmic assembly of the U4 snRNP, the interaction of the U4 snRNP with U6 RNA/RNP occurs in the nucleus; furthermore, cytoplasmic-nuclear transport of the U4 snRNP is independent of U4/U6 snRNP assembly.

Animals↗

PubMed1990

Protein-mediated nuclear export of RNA: 5S rRNA containing small RNPs in xenopus oocytes.

We have analyzed RNP formation and nucleocytoplasmic migration of 5S RNA and 5S RNA variants transcribed from microinjected genes in Xenopus oocytes. Using antisera against three different proteins we find that newly transcribed nuclear 5S rRNA transiently interacts with La antigen. The La protein is then replaced by either ribosomal protein L5 or the 5S gene-specific transcription factor IIIA (TFIIIA), and each of these two RNPs migrates out of the nucleus and accumulates in the cytoplasm. RNA molecules that are impaired in their ability to interact with L5 and TFIIIA are retained in the nucleus. Thus, L5 and TFIIIA define a new functional class of proteins involved in the nuclear export of RNA. In addition, we show that RNP migration depletes the nucleus of TFIIIA, resulting in a loss of transcription competence for newly injected 5S rRNA genes.

Animals↗

PubMed1986

Analysis of the RNA structural elements involved in the binding of the transcription factor III A from Xenopus laevis.

Xenopus laevis 5S rRNA isolated from 7S particles or transcribed in vitro is found to adopt two alternative conformations. These two conformers contain different structural elements within the major TF III A binding domain, which, when isolated as RNA fragments, still interact with the transcription factor. Chemical modification of easily accessible adenines in their N-1 position does not have any measurable effect on the binding of 5S rRNA to TF III A. These observations are in support of the idea that only a small amount of conserved sequence information is required for the binding of the transcription factor, whereas specific secondary structure features seem to be essential.

Animals↗

PubMed1976