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PubMed1978

Modification of yeast ribosomal proteins. Phosphorylation.

Two-dimensional polyacrylamide-gel electrophoretic analysis of yeast ribosomal proteins labelled in vivo with 32PO43- revealed that the proteins S2 and S10 of the 40S ribosomal subunit, and the proteins L9, L30, L44 and L45 of the 60S ribosomal subunit, are phosphorylated in vivo. Most of the phosphate groups appeared to be linked to serine residues. Teh number of phosphate groups per molecule of phosphorylated protein species ranged from 0.01 to 0.79. Since most of the phosphorylated ribosomal proteins appear to associate with the pre-ribosomal particles at a very late stage of ribosome assembly, phosphorylation is more likely to play a role in the functioning of the ribosome than in its assembly.

Amino Acids↗
PubMed1978

Modification of yeast ribosomal proteins. Methylation.

Two-dimensional polyacrylamide-gel electrophoretic analysis of yeast ribosomal proteins uniformly labelled in vivo with [methyl-3H]methionine and [1-14C]methionine revealed that four ribosomal proteins are methylated, i.e. proteins S31, S32, L15 and L41. Lysine and arginine appear to be the predominant acceptors of the methyl groups. The degree of methylation ranges from 0.09 to 0.20 methyl group per modified ribosomal protein species.

Amino Acids↗
PubMed1979

Analysis of histones from the yeast Saccharomyces carlsbergensis.

Basic chromosomal proteins were isolated from the chromatin of the yeast Saccharomyces carlsbergensis by extraction with H2SO4 and were purified by ion-exchange chromatography. Electrophoresis of the purified fraction on acetic acid/urea gels revealed the presence of four main components. These four proteins were identified as histones H2A, H2B, H3 and H4 on the basis of their amino acid composition, molecular weight and solubility properties, all of which are very similar to the corresponding properties of the various histone proteins from other eukaryotic organisms. A fifth basic protein could be isolated from yeast chromatin by extraction with HClO4. The available evidence indicates this protein to be an H1-type histone. Yeast thus appears to contain a complete set of histone proteins which are strongly homologous to the histones occurring in higher eukaryotes.

Amino Acids↗
PubMed2026

Maize Gametophytic factor loci Ga3 through Ga11 modify reproductive barriers.

Gametophytic factor (Ga) barriers are maize (Zea mays ssp. mays) reproductive barriers controlled by molecular incompatibilities between pollen and silks. Twelve distinct Ga loci have been identified in maize populations since the first genetic evidence of a Ga barrier was reported in 1901. Of the twelve, however, only three have been validated by modern molecular, functional and genomic studies: Ga1, Ga2, and Tcb1. The remaining "higher" Ga loci, spanning Ga3 to Ga11, were reported in the historical literature, but their associated phenotypes segregated in unexpected ways or disappeared over subsequent generations. Here we introduce and explore the hypothesis that the higher Ga loci represent modifiers of Ga1, Ga2, and Tcb1 barrier functions. By revisiting the historical literature, we found that barrier phenotypes fall into two phenotypic and functional categories. Phenotypically, the two categories represented healthy pollen with a silk-length effect and unhealthy pollen without a silk-length effect. These phenotypic categories were supported by genomic data; we identified candidate genes in each higher Ga locus by comparing historical linkage mapping data to the corresponding genomic sequence of maize reference line B73. We discovered candidate genes related to two broad pathways: pollen tube growth and RNA-directed DNA methylation. We conclude that the past century of evidence aligns with our hypothesis that maize loci Ga3 through Ga11 modify rather than directly control Ga barriers. This brief investigation provides a starting point for geneticists and evolutionary biologists to explore how strong reproductive barriers are shaped by epistatic interactions.

Epistasis↗
PubMed1977

Sequence of the 3'-terminal 21 nucleotides of yeast 17S ribosomal RNA.

The sequence of the 3'-terminal 21 nucleotides of 17S ribosomal RNA from the yeast Saccharomyces carlsbergensis has been determined to be (Y)G-m62A-m62A-C-U-C-G-C-G-G-A-A-G-G-A-U-C-A-U-U-AOH. This sequence shows extensive homology with the 3'-terminal sequence of 16S rRNA from Escherichia coli including the presence of the two adjacent N6-,N6-dimethyladenosines observed in the small subunit rRNA of eukaryotes as well as of many prokaryotes.

Base Sequence↗
PubMed1978

Genetic organization of the ribosomal transcription units of the yeast Saccharomyces carlsbergensis.

The genetic organization of the multiple ribosomal transcription units (RTUs) on the genome of the yeast Saccharomyces carlsbergensis was studied by electron microscopy of purified ribosomal DNA hybridized to 26S rRNA using the R-loop technique (Thomas, M., White, R.L. and Davis, R.W. (1973) Proc. Natl. Acad. Sci. U.S. 73, 2294-2298). Plasmid pBR 322, the molecular weight of which is known, was used as a standard for converting contour length of double-stranded DNA into molecular weight. The 140 yeast RTUs were found to be arrayed in tandem repeats, each repeat containing at most 0.4 X 10(6) D (about 6% of the length of the RTU) of non-transcribed spacer DNA. The repeats, in turn, are arranged in a number of clusters separated by much longer stretches of non-ribosomal DNA.

Genes↗
PubMed1979

The primary transcript of the ribosomal repeating unit in yeast.

Endgroup analysis of 37S ribosomal precursor RNA from Saccharomyces carlsbergensis has revealed that the major 5' endgroup is ppA-Up, with a molar yield of 0.8. This shows that most, if not all, 37S RNA molecules have preserved a transcriptional initiation sequence. Analysis of the 3' terminus of 37S RNA has shown the presence of a uridine rich oligonucleotide, tentatively identified as U6-8-A-NOH. This long stretch of uridines at the 3' end of 37S RNA may represent a transcriptional termination site. The two sets of data on the terminal sequences suggest that 37S ribosomal precursor RNA, if not already spliced, is a primary transcription product. Since the 3' terminus of 26S rRNA, U-U-U-G-UOH., appears to be clearly different from the 3' end of 37S RNA, we conclude that 37S ribosomal precursor RNA contains additional nucleotides 3'-distal to the 26S rRNA sequence.

Base Sequence↗
PubMed1979

Pseudouridylation of yeast ribosomal precursor RNA.

The pseudouridylation of ribosomal RNA of Saccharomyces carlsbergensis was investigated with respect to its timing during the maturation of rRNA and its sequence specificity. Analysis of 37-S RNA, the common precursor to 17-S, 5.8-S and 26-S rRNA and most probably the primary ribosomal transcript, shows that this RNA molecule contains already most if not all of the 36-37 pseudouridine residues found in the mature rRNAs. Thus pseudouridylation is, like 2'-0-ribosemethylation, an early event in the maturation of rRNA, taking place immediately after, or even during, transcription. The data presented show that the non-conserved sequences of 37-S precursor rRNA contain very few pseudouridine residues if any. The pseudouridine residues within the rRNA sequences are apparently clustered to a certain degree as can inferred from the occurrence of a single oligonucleotide containing 3 pseudouridines, which was obtained by digestion of 26-S rRNA with ribonuclease T1.

Base Sequence↗
PubMed1979

Extrachromosomal circular ribosomal DNA in the yeast Saccharomyces carlsbergensis.

Purified ribosomal DNA from Saccharomyces carlsbergensis contains a small proportion of circular DNA molecules with a contour length of 3 micron or integral multiples thereof. Hybridization of yeast ribosomal DNA with 26 S rRNA, using the R-loop technique, reveals that these circular molecules contain sequences complementary to yeast ribosomal RNA. We suggest that these extrachromosomal rRNA genes may be intermediates in the amplification of rRNA genes in yeast.

DNA, Circular↗
PubMed1977

Terminal nucleotide sequences of 17-S ribosomal RNA and its immediate precursor 18-S RNA in yeast.

The 5' and 3'-terminal nucleotide sequences of 17-S rRNA and its immediate precursor 18-S RNA from the yeast Saccharomyces carlsbergensis have been analysed. Identification of the terminal oligonucleotides, as present in Ti ribonuclease digests, was performed by diagonal procedures. The major (molar yield 0.9) 5'-terminal oligonucleotide (molar yield 0.15) with the overall composition pU (U2,C2)G was observed. 18-S precursor RNA was found to contain the same 5'-terminal sequences as 17-S rRNA. However, the 3'-terminal sequences of the two types of RNA appeared to be different. The 17-S rRNA yields the oligonucleotide A-U-C-A-U-U-AOH while at least half of the 18-S RNA molecules contain the sequence U-U-U-C-A-A-U-AOH. In addition 18-S RNA yields several minor 3'-terminal oligonucleotides which appear to be structurally related to the major 3'-terminal sequence. These results demonstrate that the extra nucleotides in 18-S RNA relative to 17-S RNA are located exclusively at the 3'-terminus of the 18-S RNA molecule. The possibility that the 3'-terminal nucleotide sequence of 18-S RNA plays a role in the maturation process is discussed.

Base Sequence↗
PubMed1977

Secondary methylation of yeast ribosomal precursor RNA.

The timing of methylation of the ribosomal sequences of ribosomal precursor RNA (pre-rRNA) from the yeast Saccharomyces carlsbergensis was investigated by fingerprint analysis of the methylated oligonucleotides derived from the various precursors. From the total of 37 ribose and 6 base-methyl groups found in 26-S rRNA, the two copies of the base-methylated nucleoside m3U as well as the doubly methylated sequence Um-Gm psi are not yet present in 37-S RNA, the predominant common precursor of 26-S and 17-S rRNA. Introduction of these methyl groups into the ribosomal sequences appears to take place at the level of 29-S pre-rRNA, the immediate precursor to 26-S rRNA. From the total of 18 ribose-methylated and 6 base-methylated nucleosides found in 17-S rRNA, the latter group (one copy of m7G, the m62A-m62A- sequence and the hypermodified methylated nucleoside "mX") is completely missing in 37-S pre-rRNA. The methyl group of m7G is introduced into 18-S pre-rRNA, the direct precursor of 17-S rRNA, in the nucleus. The -m62A-m62A- sequence is methylated after transport of the 18-S pre-rRNA to the cytoplasm prior to the final maturation into 17-S rRNA.

Base Sequence↗
PubMed1977

Transcriptional units for ribosomal proteins in yeast.

The effects of ultraviolet irradiation on the rates of synthesis of individual ribosomal proteins in yeast were examined and compared with the ultraviolet sensitivities of the synthesis of other yeast proteins. It was found that the synthesis of yeast ribosomal proteins is much more sensitive to ultraviolet irradiation than that of other yeast cellular proteins. Taking into account the half-life of yeast mRNA, the results obtained indicate that the genes coding for ribosomal proteins form part of long transcriptional units, which are much longer than the DNA stretch needed to code for a ribosomal protein of average molecular weight. Saturation hybridization of total poly(A)-containing mRNA with yeast nuclear DNA revealed that as much as 30% of DNA is complementary to yeast mRNA. Thus, the primary transcript of a protein gene on the average is about 1.7 times the length of the actual messenger. On the basis of the various experimental data we suggest a clustering of the yeast ribosomal protein genes in a number of common transcriptional units.

DNA↗
PubMed1978

Quantitative analysis of the protein composition of yeast ribosomes.

The molecular weights of the individual yeast ribosomal proteins were determined. The ribosomal proteins from the 40-S subunit have molecular weights ranging from 11 800 to 31 000 (average molecular weight = 21 300). The molecular weights of the 60-S subunit proteins range from 10 000 to 48 400 (average molecular weight = 21 800). Stoichiometric measurements, performed by densitometric scanning on ribosomal proteins extracted from high-salt dissociated subunits revealed that isolated ribosomal subunits contain, besides some protein species occurring in submolar amounts, a number of protein species which are present in multiple copies: S13, S27, L22, L31, L33, L34 and L39. The mass fractions of the ribosomal proteins which were found to be present on isolated ribosomes in non-unimolar amounts, were re-examined by using an isotope dilution technique. Applying this method to proteins extracted from mildely isolated 80-S ribosomes, we found that some protein species such as S32, S34 and L43 still are present in submolar amounts. On the other hand, however, we conclude that some other ribosomal proteins, in particular the strongly acidic proteins L44 and L45 get partially lost during ribosome dissociation. Proteins L44/L45 appears to be present on 80-S ribosomes in three copies.

Electrophoresis, Polyacrylamide Gel↗
PubMed1978

Non-ribosomal nucleotide sequences in 7-S RNA, the immediate precursor of 5.8-S ribosomal RNA in yeast.

The topography and the length of the non-ribosomal sequences present in 7-S RNA, the immediate precursor of 5.8-S ribosomal RNA, from the yeast Saccharomyces carlsbergensis were determined by analyzing the nucleotide sequences of the products obtained after complete digestion of 7-S RNA with RNase T1. The results show that 7-S RNA contains approximately 150 non-ribosomal nucleotides. The majority (90%) of the 7-S RNA molecules was found to have the same 5'-terminal pentadecanucleotide sequence as mature 5.8-S rRNA. The remaining 10% exhibited 5'-terminal sequences identical to those of 5.9-S RNA, which has the same primary structure as 5.8-S rRNA except for a slight extension at the 5' end [Rubin, G.M. (1974) Eur. J. Biochem. 41, 197--202]. These data show that the non-ribosomal nucleotides present in 7-S RNA are all located 3'-distal to the mature 5.8-S rRNA sequence. Moreover, it can be concluded that 5.9-S RNA is a stable rRNA rather than a precursor of 5.8-S rRNA. The 3'-terminal sequence of 5.8-S rRNA (U-C-A-U-U-UOH) is recovered in a much longer oligonucleotide in the T1 RNase digest of 7-S RNA having the sequence U-C-A-U-U-U-(C-C-U-U-C-U-C)-A-A-A-C-A-(U-U-C-U)-Gp. The sequences enclosed in brackets are likely to be correct but could not be established with absolute certainty. The arrow indicates the bond cleaved during processing. The octanucleotide sequence -A-A-A-C-A-U-U-C- located near the cleavage site shows a remarkable similarity to the 5'-terminal octanucleotide sequence of 7-S RNA (-A-A-A-C-U-U-U-C-). We suggest that these sequences may be involved in determining the specificity of the cleavages resulting in the formation of the two termini of 5.8-S rRNA.

Base Sequence↗
PubMed1979

[Von Recklinghausen's neurofibromatosis and skeletal changes].

Two cases of von Recklinghausen's neurofibromatosis with osseous involvement are described and compared with cases in the literature. The most important skeletal lesions are dysplastic defects of the skull, macrocranium, deformities of the vertebral column with associated lesions of the vertebral bodies, congenital bowing, pseudarthrosis, length disparity and periostal dysplasias of the extremities, and congenital anomalies, erosions and cysts in the remaining skeleton.

Adult↗
PubMedDate not supplied

[Size, structure, and dynamics of bile salt/lecithin mixed micelles (author's transl)].

The structure and size of lecithin/sodium glycocholate mixed micelles was investigated by quasi-elastic laser light scattering and spin label techniques. The investigations are in accordance with a bilayer model for these micelles. The order parameter and the phase transition enthalpy of the micellar bilayer were determined. The lateral and rotational diffusion constants of label molecules are compared with the corresponding diffusion constants in liposomes.

Chemical Phenomena↗