PubMed Health⌕ Search

Biomedical subjects

P K Wellauer

Publications and source records attributed to P K Wellauer.

At least 37 records · Page 2Linked to original sources
PubMed1981

Mouse liver and salivary gland alpha-amylase mRNAs differ only in 5' non-translated sequences.

The sequence of 1,773-nucleotide major and 1,806-nucleotide minor mouse liver alpha-amylase mRNAs differ only with respect to approximately 30 additional residues at the extreme 5' terminus of the minor species. Comparison of the liver alpha-amylase mRNAs with their salivary gland counterpart reveals that these mRNAs share identical coding and 3'-noncoding sequences, but contain distinct 5'-terminal residues. These data suggest that all three mRNAs might be transcribed from the same gene.

Amylases↗
PubMed1977

Intermolecular duplexes in heterogeneous nuclear RNA from HeLa cells.

Rapidly sedimenting hnRNA complexes contain regions of stable intermolecular duplex. Disruption of such complexes, as judged by a reduction in sedimentation rate, requires conditions sufficient to denature the duplex regions. Rapidly sedimenting molecules reappear only when the complementary sequences reanneal-that is, the formation of such complexes is dependent upon time and the concentration of homologous RNA. These experiments lead us to the conclusion that rapidly sedimenting hnRNA complexes consist of two or more largely single-stranded RNA molecules held together by short duplex regions. Precisely such structures have been visualized in the electron microscope. Rapidly sedimenting fractions of native nuclear RNA from preparative sucrose gradients consist primarily of large, multi-molecular complexes interconnected by duplex regions averaging 300 base pairs in length. Exposure of the RNA to severely denaturing conditions eliminates such complexes. Reannealing of the RNA reconstitutes complexes which are indistinguishable from those observed in preparations before denaturation.

Base Sequence↗
PubMed1977

The structural organization of ribosomal DNA in Drosophila melanogaster.

The genes coding for the large rRNAs (rDNA) were purified from Drosophila melanogaster embryos by two different methods. Purified rDNA was analyzed by gel electrophoresis after digestion with restriction endonucleases and by electron microscopy. Each repeating unit of rDNA consists of a gene region that codes for a transcript which includes the 18S and 28S rRNA sequences plus a nontrascribed spacer. Analysis of rRNA/rDNA hybrids in the electron microscope reveals that two types of repeating units exist in the rDNA from this fly. One of these is characterized by insertions of various lengths within the 28S gene. Insertions range in size from about 0.5 kilo base pairs (kb) to 6.0 kb and occur in distinct size classes which are multiples of 0.5 kb. Figure 10 summarizes the structure of the rDNA repeating unit. Repeats with insertions constitute about two thirds, and repeats without insertions about one third of all repeating units in the sample studied where 86% of the rDNA is derived from the X chromosome nucleolus organizer. Statistical analysis of pairs of of nearest-neighbor repeats demonstrates that repeats with and without insertions are interspersed in the X chromosome nucleolus organizer, and that scrambling is close to that expected for random arrangement. Insertions are the major source of length heterogeneity in this rDNA. A minor length heterogeneity also exists in thie nontranscribed spacer of Drosophila rDNA as demonstrated by heteroduplex mapping of restriction fragments in the electron microscope.

Chromosome Mapping↗
PubMed1976

A reinvestigation of 5' leads to 3' polarity in 40S ribosomal RNA precursor of Xenopus laevis.

The 5' leads to 3' polarity of the 40S precursor rRNA molecule relative to the location of the 18S and 28S RNA regions in the precursor has been reinvestigated. Fragments of rDNA derived by the restriction endonuclease EcoRI and cloned in E. coli were partially digested with the exonuclease induced by bacteriophage lambda and with exonuclease III from E. coli. The resulting rDNA fragments with single-stranded tails were hybridized separately with 18S and 28S rRNA, and the formation of the hybrid was monitored by determination of radioactivity and by electron microscopy. Since the location of the EcoRI sites in rDNA is known, and the specificity of the two exonucleases for 5' and 3' ends of DNA strands has been established, the hybridization of the different partially digested rDNA fragments with either 18S or 28S rRNA could be interpreted in terms of polarity of the coding strand of rDNA, and consequently of the RNA (see models in Figure 1). The results supports the following model for the rRNA precursor moleculre: 5' end-transcribed space-18S gene-transcribed space-28S gene-3' end.

Animals↗