Characterization of amber and ochre suppressors in Salmonella typhimurium.

Amber and ochre suppressor mutations in Salmonella typhimurium were selected. The amino acid insertions directed by the suppressors were inferred from suppression patterns of Escherichia coli lacI amber mutations. These amber mutations only respond to nonsense suppressors that direct the insertion of particular amino acids. Four Salmonella amber suppressors characterized insert serine, glutamine, tyrosine, and (probably) leucine. Of the three ochre suppressors characterized, two direct the insertion of tyrosine and one directs that of lysine. Of the three amber and two ochre suppressors which have been mapped by phage P22 cotransduction, all are located in the same relative position on the Salmonella map as the analogous E. coli suppressors are on the E. coli map.     

The gripping nature of ochre: the association of ochre with Howiesons Poort adhesives and Later Stone Age mastics from South Africa

This contribution provides direct evidence for the use of ochre in adhesive recipes during the Howiesons Poort of South Africa. Stone segments from two KwaZulu-Natal sites were microscopically analyzed to document ochre and resin microresidue occurrences. These microresidues show a clear distribution pattern on the tool portions that are associated with hafting. Results from a separate quartz and crystal-quartz sample may indicate that different adhesive recipes were applied to different raw materials. A possible functional application for ochre in association with Later Stone Age mastics is also explored. The evidence and suggestions presented here expand our understanding of the versatility, use, and value of pigmentatious materials in prehistory; it is not viewed as an alternative or replacement hypothesis for its possible symbolic role during the late Pleistocene.     

Mutagenesis in Escherichia coli. V. Attempted interconversion of ochre and amber suppressors and mutational instability due to an ochre suppressor

Summary A possible quantitative system for the interconversion of ochre and amber suppressors was studied in Escherichia coli WU36-10, a strain in which a leucine requirement is suppressed by amber suppressors and a tyrosine requirement is suppressed by ochre suppressors. The conversion of am Sup-2⁺ to oc Sup-2⁺ occurred at rates similar to those for the de novo induction of such suppressors, both spontaneously and after ultraviolet or gamma irradiation. Both induction and conversion of suppressors showed the phenomenon of mutation frequency decline after ultraviolet light. Conversions in the opposite direction from oc Sup-2⁺ to am Sup-2⁺ were, however, not detected in unmutagenised populations of oc Sup-2⁺ strains derived either by conversion from an am Sup-2⁺ strain or de novo from the parental WU36-10, nor were they detected after treatment with ultraviolet light, gamma radiation or 2-aminopurine. If the conversion of oc Sup-2⁺ to am Sup-2⁺ occurs at all, it is at a rate very considerably lower than that for the conversion of am Sup-2⁺ to oc Sup-2⁺. Some Tyr⁺ oc Sup-2⁺ mutants demonstrated mutation rates c. 100 times greater than those of WU36-10 for mutation to Leu⁺ spontaneously and after ultraviolet or gamma radiation. Possible explanations of this are discussed.     

古人类对赭石的利用行为在其演化中的意义

长期以来赭石利用行为被视为人类行为现代性的标志之一,受到国内外考古学界的普遍关注。本文回溯和梳理了全球背景下赭石利用的起源、发展及其与人类演化史的关系。在现代人广泛分布于全球之后,赭石利用行为更加丰富和多样化地出现在各地,然而现有考古证据表明该行为并不是解剖学意义上的现代人突变性的发明。赭石利用不能被单纯地定义为现代人行为,而应是有着长久演化积累的现代性行为之一。在长期传播与演化过程中,赭石的功能从意识形态、艺术表达等逐渐扩展到作为矿物成分被用于实际生产生活。赭石的利用历史可追溯到中更新世中期,但其广泛分布仍与晚更新世以来现代人的广泛扩散直接相关,对于理解现代人的意识形态、社会组织方式以及艺术表达、精神文化发展都具有重要的意义。国内目前所发表的相关考古学证据相对较少,以下马碑遗址为代表的材料,也恰处于现代人在全球广泛扩散的窗口期,并伴有进步的细小石器镶嵌使用的证据,成为认识东亚现代人行为的关键性考古证据。     

Serine substitutions caused by an ochre suppressor in yeast.

The suppressor SUQ5 in yeast can cause the production of approximately 10 to 20% of the normal amount of iso-l-cytochrome c when coupled to the ochre (UAA) mutants cyc1–2 and cyc1–72. The iso-l-cytochromes c contain residues of serine at positions that correspond to the sites of the ochre codons. SUQ5 is efficient only in strains having the non-Mendelian factor ψ⁺, although the low amount of suppressed iso-l-cytochrome c from a ψ⁻SUQ5 cyc1–72 strain was also shown to contain serine at the ochre site. Thus SUQ5 differs from the eight other characterized suppressors of UAA in yeast, which were previously shown to insert residues of tyrosine at ochre sites (Gilmore et al., 1971) and which are only effective in strains haying the non-Mendelian factor ψ⁻, since they generally cause inviability in the ψ⁺ state. Like the tyrosine-inserting suppressors, SUQ5 can also act on another ochre allele cyc1–9, but with a very low efficiency of approximately 0.4%, while it does not appear to act at all on amber (UAG) mutants. SUQ5 was found to be 6.4 cM (centiMorgans) from tyr7 on chromosome XVI. It is suggested that the gene product of SUQ5 is serine tRNA.     

Isolation of glutamate-inserting ochre suppressor mutants of Salmonella typhimurium and Escherichia coli.

Glutamate-inserting ochre suppressors have been identified among late-arising, spontaneous revertants of a hisG428 mutant of Salmonella typhimurium and an argE3 mutant of Escherichia coli. The S. typhimurium suppressors mapped in the tRNA2(Glu) gene gltU at 82 min; those in E. coli were found to be in tRNA2(Glu) genes gltW at 56 min, gltU at 85 min, and gltT at 90 min.     

Suppression of amber and ochre rII mutants of bacteriophage T4 by streptomycin

Orias, E. (University of California, Santa Barbara), and T. K. Gartner. Suppression of amber and ochre rII mutants of bacteriophage T4 by streptomycin. J. Bacteriol. 91:2210-2215. 1966.-Streptomycin-induced suppression of amber and ochre rII mutants of phage T4 was studied in a streptomycin-sensitive strain of Escherichia coli and four nearly isogenic streptomycin-resistant derivatives of this strain, in the presence and in the absence of an ochre suppressor. Most of the 12 rII mutants tested were suppressed by streptomycin in the streptomycin-sensitive su(-) strain. This streptomycin-induced suppression in the su(-) strain was eliminated by the independent action of at least two of the four nonidentical mutations to streptomycin resistance. In two of the su(+)str-r strains, streptomycin markedly augmented the suppression caused by the ochre suppressor. In those su(-)str-r hosts in which significant streptomycin-induced suppression could be measured, the amber mutants were more suppressible than the ochre mutants.     

supN ochre suppressor gene in Escherichia coli codes for tRNALys.

We describe the cloning and nucleotide sequence of a new tRNALys gene, lysV, in Escherichia coli. An ochre suppressor allele of this gene, supN, codes for a tRNALys with anticodon UUA, presumably derived by a single base change from a wild-type UUU anticodon. The sequence of the supN tRNALys is identical to the sequence of ochre suppressor tRNAs encoded by mutant alleles at the lysT locus. This locus, which contains the two previously known tRNALys genes of E. coli, is located far from the lysV locus on the chromosome.     

Synthesis of an ochre suppressor tRNA gene and expression in mammalian cells.

We have used site-specific mutagenesis to change the anticodon of a Xenopus laevis tyrosine tRNA gene so that it would recognize ochre codons. This tRNA gene is expressed when amplified in monkey cells as part of a SV40 recombinant and efficiently suppresses termination at both the ochre codon separating the adenovirus 2 hexon gene from a 23-kd downstream gene and the ochre codon at the end of the NS1 gene of influenza virus A/Tex/1/68. Termination at an amber codon of a NS1 gene of another influenza virus strain was not suppressed by the (Su+) ochre gene suggesting that in mammalian cells amber codons are not recognized by ochre suppressor tRNAs. Finally, microinjection into mammalian cells of both (Su+) ochre tRNA genes and selectible genes containing ochre nonsense mutations gives rise to colonies under selective conditions. We conclude that it should be possible to isolate a wide assortment of mammalian cell lines with ochre suppressor activity.     

Position of the mutation in beta-galactosidase ochre mutant U118.

The Escherichia coli lacZ ochre mutant strain U118 was converted to an amber mutant and suppressed with supF, which inserts tyrosine. Enzymatically active beta-galactosidase was isolated. It contained tyrosine at residue number 17 instead of glutamic acid as in wild type.     

In vivo translation of amber and ochre codons in Escherichia coli

Summary By making certain assumptions, we have provided evidence which indicates that: amber and ochre codons function in vivo, the bulk of the E. coli mRNA is polycistronic, intercistronic space may correspond to no more than 12–24 nucleotides and ochre is used twenty five times more frequently than amber, for chain termination.     

Shells and ochre in Middle Paleolithic Qafzeh Cave,Israel: indications for modern behavior

Qafzeh Cave, the burial grounds of several anatomically modern humans, producers of Mousterian industry, yielded archaeological evidence reflecting their modern behavior. Dated to 92 ka BP, the lower layers at the site contained a series of hearths, several human graves, flint artifacts, animal bones, a collection of sea shells, lumps of red ochre, and an incised cortical flake. The marine shells were recovered from layers earlier than most of the graves except for one burial. The shells were collected and brought from the Mediterranean Sea shore some 35 km away, and are complete Glycymeris bivalves, naturally perforated. Several valves bear traces of having been strung, and a few had ochre stains on them.     

Amber, ochre and opal suppressor tRNA genes derived from a human serine tRNA gene.

Amber, ochre and opal suppressor tRNA genes have been generated by using oligonucleotide directed site-specific mutagenesis to change one or two nucleotides in a human serine tRNA gene. The amber and ochre suppressor (Su+) tRNA genes are efficiently expressed in CV-1 cells when introduced as part of a SV40 recombinant. The expressed amber and ochre Su+ tRNAs are functional as suppressors as demonstrated by readthrough of the amber codon which terminates the NS1 gene of an influenza virus or the ochre codon which terminates the hexon gene of adenovirus, respectively. Interestingly, several attempts to obtain the equivalent virus stock of an SV40 recombinant containing the opal suppressor tRNA gene yielded virus lacking the opal suppressor tRNA gene. This suggests that expression of an efficient opal suppressor derived from a human serine tRNA gene is highly detrimental to either cellular or viral processes.     

Nucleotide sequence and evolution of the rat mitochondrial cytochrome b gene containing the ochre termination codon

The nucleotide sequences of the genes for cytochrome b and three potential transfer RNAs (tRNAPro, tRNAThr and tRNAGlu) in cloned rat mitochondrial DNA were determined. The derived amino acid sequence of the cytochrome b protein from the light strand indicated that the C-terminal amino acid is asparagine and the ochre termination codon is encoded in the DNA, in contrast to the the lack of termination codon in the reading frame of human [Anderson et al., Nature 290 (1981) 457] or mouse [Bibb et al., Cell 26 (1981) 167] mitochondrial DNA. The first ATG codon of the cytochrome b gene was spaced five nucleotides from the 5'-end of the tRNAGlu gene on the heavy strand. There was a single nucleotide spacing between the termination codon of the cytochrome b gene and the 5' end of the tRNAThr gene in the light strand. There was also a single nucleotide spacing between the 3'-end of the tRNAThr gene and the 3'-end of the tRNAPro gene on the heavy strand. The amino acid and nucleotide sequences of the cytochrome b genes of mammals and yeast [Nobrega and Tzagoloff, J. Biol. Chem. 255 (1980) 9828] were compared to reveal structural differences in two very different species. At the same time, amino acid substitutions in particular regions of the mammalian gene corresponding to the exon-intron boundaries in the yeast gene were noted. These genetic features are discussed in relation to the extreme compression of genetic information in the mammalian mitochondrial genome as related to the evolution of the gene organization and its sequence.