Regressive periods in primate behavioral development with reference to other mammals

Studies on behavioral development in 12 species of monkeys indicate normal fluctuations of high frequency of nipple contact. These periods decrease in intensity as the infant develops and occur at similar times in development in the 12 species. Literature on 11 species of primates and three species of non-primates indicates similar regressions in mother-infant contact, which implies a common genetic basis for the phenomenon.     

Expression of the gene for the polyoma small T antigen in Escherichia coli.

A cloned segment of the polyoma virus genome encoding the small T antigen has been fused, in the correct phase for translation, to the 5' end of the beta-galactosidase gene. The hybrid gene, cloned in Escherichia coli, produces a protein resembling the small T antigen.     

Trinucleotide cassettes increase diversity of T7 phage-displayed peptide library

Background  

Amino acid sequence diversity is introduced into a phage-displayed peptide library by randomizing library oligonucleotide DNA. We recently evaluated the diversity of peptide libraries displayed on T7 lytic phage and M13 filamentous phage and showed that T7 phage can display a more diverse amino acid sequence repertoire due to differing processes of viral morphogenesis.     

The unaccounted yet abundant nitrous oxide-reducing microbial community: a potential nitrous oxide sink

Nitrous oxide (N₂O) is a major radiative forcing and stratospheric ozone-depleting gas emitted from terrestrial and aquatic ecosystems. It can be transformed to nitrogen gas (N₂) by bacteria and archaea harboring the N₂O reductase (N₂OR), which is the only known N₂O sink in the biosphere. Despite its crucial role in mitigating N₂O emissions, knowledge of the N₂OR in the environment remains limited. Here, we report a comprehensive phylogenetic analysis of the nosZ gene coding the N₂OR in genomes retrieved from public databases. The resulting phylogeny revealed two distinct clades of nosZ, with one unaccounted for in studies investigating N₂O-reducing communities. Examination of N₂OR structural elements not considered in the phylogeny revealed that the two clades differ in their signal peptides, indicating differences in the translocation pathway of the N₂OR across the membrane. Sequencing of environmental clones of the previously undetected nosZ lineage in various environments showed that it is widespread and diverse. Using quantitative PCR, we demonstrate that this clade was most often at least as abundant as the other, thereby more than doubling the known extent of the overall N₂O-reducing community in the environment. Furthermore, we observed that the relative abundance of nosZ from either clade varied among habitat types and environmental conditions. Our results indicate a physiological dichotomy in the diversity of N₂O-reducing microorganisms, which might be of importance for understanding the relationship between the diversity of N₂O-reducing microorganisms and N₂O reduction in different ecosystems.     

A carboxy-terminal deletion impairs the assembly of GroEL and confers a pleiotropic phenotype in Escherichia coli K-12.

A series of COOH-terminal deletions of the chaperonin GroEL have been examined for effects in vivo at haploid copy number on the essential requirement of GroEL for cell growth. Strains with a deletion of up to 27 COOH-terminal amino acids were viable, but not viable strain could be isolated with a deletion of 28 or more codons. When substitutions were placed in the COOH-terminal amino acid Val-521 of the 27-amino-acid-deleted (delta 27) mutant, we found variable effect--Trp and Glu led to inviability, whereas Arg and Gly were viable but slow growing. The effects of the Arg substitution plus deletion (V521R delta) were examined in more detail. Whereas the delta 27 mutant with the wild-type residue Val-521 grew as well as a strain with wild-type GroEL, the V521R delta mutant strain (groEL202) exhibited a broad range of phenotypic defects. These include slow growth; filamentous morphology; a defect in plating lambda; absence of activity of expressed human ornithine transcarbamylase, as seen in other GroEL mutants; and several newly observed defects, such as absence of motility, sensitivity to UV light and mitomycin, a defect in one mode of specialized transduction, and inability to grow on rhamnose. Sucrose gradient analysis of extracts from the V521R delta cells showed a substantially reduced level of GroEL sedimenting at the normal 20S position of the assembled tetradecamer and a relatively large amount of more lightly sedimenting subunits. This indicates that the substitution-deletion mutation interferes with oligomeric assembly of GroEL into its functional form. This is discussed in light of the recently determined crystal structure of GroEL.     

The Drosophila RNA methyltransferase, DmHen1, modifies germline piRNAs and single-stranded siRNAs in RISC

Small silencing RNAs repress gene expression by a set of related mechanisms collectively called RNA-silencing pathways [1, 2]. In the RNA interference (RNAi) pathway [3], small interfering mRNA (siRNAs) defend cells from invasion by foreign nucleic acids, such as those produced by viruses. In contrast, microRNAs (miRNAs) sculpt endogenous mRNA expression [4]. A third class of small RNAs, Piwi-interacting RNAs (piRNAs), defends the genome from transposons [5-9]. Here, we report that Drosophila piRNAs contain a 2'-O-methyl group on their 3' termini; this is a modification previously reported for plant miRNAs and siRNAs [10] and mouse and rat piRNAs [11, 12, 13]. Plant small-RNA methylation is catalyzed by the protein HEN1 [10, 14, 15]. We find that DmHen1, the Drosophila homolog of HEN1, methylates the termini of siRNAs and piRNAs. Without DmHen1, the length and abundance of piRNAs are decreased, and piRNA function is perturbed. Unlike plant HEN1, DmHen1 acts on single strands, not duplexes, explaining how it can use as substrates both siRNAs-which derive from double-stranded precursors-and piRNAs-which do not [8, 13]. 2'-O-methylation of siRNAs may be the final step in assembly of the RNAi-enzyme complex, RISC, occurring after an Argonaute-bound siRNA duplex is converted to single-stranded RNA.     

Localization of DNA sequences in region Xp21 of the human X chromosome: Search for molecular markers close to the duchenne muscular dystrophy locus

Panels of somatic cell hybrid lines carrying various structural rearrangements of the human X chromosome short arm were analyzed with 21 X-chromosome-specific cloned DNA fragments. We mapped these molecular markers to five different regions of the short arm of the X chromosome. The results were confirmed by gene-dosage studies of human lymphoblasts with structurally abnormal X chromosomes. The ornithine transcarbamylase gene and four anonymous DNA sequences map within band Xp21, flanking the presumed locus for Duchenne muscular dystrophy.