Messenger RNA metabolism of animal cells: possible involvement of untranslated sequences and mRNA-associated proteins

The past several years have seen a virtual revolution in the study of eukaryotic mRNA. Among the notable recent achievements are the positive identification of mRNA precursors in HnRNA, the enumeration of the DNA sequences from which mRNA is transcribed, and the finding that mRNA in cultured cells is much more stable than was previously believed. One of most far-reaching discoveries has been the finding that mRNA in eukaryotes contains poly A. This discovery, aside from providing a powerful tool for mRNA isolation, has generated a large body of research into the properties and metabolism of poly A itself. In addition, the finding of a poly A-associated protein has given a renewed stimulus to the study of proteins associated with mRNA. This review is devoted to a discussion of these and related achievements, and some of their implications     

A genus-level supertree of the Dinosauria

One of the ultimate aims of systematics is the reconstruction of the tree of life. This is a huge undertaking that is inhibited by the existence of a computational limit to the inclusiveness of phylogenetic analyses. Supertree methods have been developed to overcome, or at least to go around this problem by combining smaller, partially overlapping cladograms. Here, we present a very inclusive generic-level supertree of Dinosauria (covering a total of 277 genera), which is remarkably well resolved and provides some clarity in many contentious areas of dinosaur systematics.     

Cid13 is a cytoplasmic poly(A) polymerase that regulates ribonucleotide reductase mRNA

Fission yeast Cid13 and budding yeast Trf4/5 are members of a newly identified nucleotidyltransferase family conserved from yeast to man. Trf4/5 are thought to be essential DNA polymerases. We report that Cid13 is a poly(A) polymerase. Unlike conventional poly(A) polymerases, which act in the nucleus and indiscriminately polyadenylate all mRNA, Cid13 is a cytoplasmic enzyme that specifically targets suc22 mRNA that encodes a subunit of ribonucleotide reductase (RNR). cid13 mutants have reduced dNTP pools and are sensitive to hydroxyurea, an RNR inhibitor. We propose that Cid13 defines a cytoplasmic form of poly(A) polymerase important for DNA replication and genome maintenance.     

Cytological Detection of the c25H Deletion Involving the Albino (c) Locus on Chromosome 7 in the Mouse

A deletion of the albino (c) locus on mouse chromosome 7 has been demonstrated using Q- and G-banding methods in a mouse heterozygous for the radiation-induced lethal albino allele, c(25H). The deletion, which is thought to be 1-6 cM long, represents about 7.6% of the length of the metaphase chromosome.     

Ultradian rhythmic models of blood pressure variation in normal human daily life

To examine levels and variance structure of systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR), we measured those 3 variables every 7.5 min for 24 h (approximately 192 samples each subject) by ambulatory monitoring in 2 nominated groups of normal volunteers: younger (Y; 8 men, 5 women, 24-44 years) and older (O; 13 men, 12 women, 50-95 years). Y and O did not differ in either sleep or wake means for HR and DBP. Mean SBP in O was 17 mm Hg higher than in Y during wakefulness. Thirty-four subjects had significant low frequency variations (presumably the circadian rhythm) in SBP, DBP and HR, regardless of age. A periodic model fitting the time series required a 9 h feature (rhythm) for Y and O in DBP for best reduction of mean square error. In addition, O regularly showed 3 h features in both SBP and DBP, a 6 h feature in DBP and a 9 h feature in SBP, which were absent in Y. Our results suggest that low-power ultradian rhythms may appear in both SBP and DBP after age 50, and possibly serve as dynamic markers of normal cardiovascular aging.     

On the Trail of Atmospheric Mutagens and Carcinogens: A Combined Chemical/Microbiological Approach

Major ecological problems of our polluted troposphere includeairborne toxic chemicals, acid rain and photochemical smog,all three of which are now recognized as being closely relatedchemical phenomena. We also recognize that inorder to developcost-effective strategies for their control, which protect publichealth and the environment, there must be close scientific interactionsbetween chemists and biological scientists. For example, ofrapidly emerging importance is the development of risk assessmentevaluations for specific aspects of each of these problem areas.In preparing such assessments, chemists must define the "exposure,"and biological scientists the "effects." In this paper, I discuss an example of how such close interactionsproved indispensible in our search for atmospheric mutagensand carcinogens. Thus, an integrated chemical/ microbiologicalprocedure for the isolation and identificationof particulatechemical mutagens in respirable diesel soot and ambient particlesis described. Emphasis is placed on our use of the short-term,Ames Salmonella typhimurium bacterial mutagenicity test as arapid, and relatively inexpensive, means of following the biologicalactivities of these environmental mutagens through the chemicalsteps of their separation, isolation and identification fromhighly complex environmental samples. Possible mechanisms offormation of these particulate mutagens are discussed. Theyinclude the reactions of polycyclic aromatic hydrocarbons presenton the surfaces of combustion-generated particles with gaseousco-pollutants such as nitrogen dioxide plus nitric acid, andozone. In discussing this research on a societally "relevant" problem,we illustrate the importance of "Science as a Way of Knowing."We further suggest that this integrated approach to scientificproblem solving by chemical and biological scientists mightserve as an example of a discussion topic on human ecology forundergraduate courses in the natural sciences.