The completion of human genome sequencing in April 2003 marked the beginning of a new era for modern biology. Since that time, the impact of having the human sequence in hand has been nothing short ...of tremendous. The attainment of this goal, which many have compared to landing a man on the moon, will obviously have a profound effect on how biological and biomedical research will be conducted in the future. The intelligent use of sequence data from humans and other organisms, along with recent technological innovation fostered by the Human Genome Project, has already led to important advances in our understanding of diseases that have a genetic basis. More importantly, the advent of the genomic era will have a profound effect on how health care is delivered from this point forward. This lecture will provide an overview of current research themes in genomics and bioinformatics, all of which are aimed at understanding the genetic factors influencing risk for complex diseases. These efforts include whole-genome association approaches to common disease, large-scale clinical genotyping projects, the comprehensive identification of the structural and functional components in the human genome (the ENCODE Project), the Cancer Genome Atlas, and new advances in the area of chemical genomics. These research efforts, all of which rely on cutting-edge genomic and bioinformatics approaches, have already begun to yield important insight into genetic pathways that make us more susceptible to genetic disorders. These findings, in turn, are establishing an important groundwork for the discovery of new molecular targets for diagnosis, treatment, and prevention of human disease.
Ral GDP dissociation stimulator (RalGDS) and its family members RGL, RLF and RGL2 are involved in Ras and Ral signaling pathways as downstream effector proteins. Here we report the precise ...localization and cloning of two forms of human
RGL gene differing at the amino terminus. Transcript A, cloned from liver cDNA libraries has the same amino terminus as the mouse RGL, whereas transcript B cloned from brain has a substitution of 45 amino acids for the first nine amino acids. At the genomic level, exon 1 of transcript A is replaced by two alternative exons (1B1 and 1B2) in transcript B. Both forms share exons 2 through 18. The human RGL protein shares 94% amino acid identity with the mouse protein. Northern blot analysis shows that human RGL is expressed in a wide variety of tissues with strong expression being seen in the heart, brain, kidney, spleen and testis.
Recent advances in sequencing technology have led to a rapid accumulation of mitochondrial DNA (mtDNA) sequences, which now represent the wide spectrum of animal diversity. However, one animal phylum ...– Ctenophora – has, to date, remained completely unsampled. Ctenophores, a small group of marine animals, are of interest due to their unusual biology, controversial phylogenetic position, and devastating impact as an invasive species. Using data from the
Mnemiopsis leidyi
genome sequencing project
,
we PCR amplified and analyzed its complete mitochondrial (mt-) genome. At just over 10kb, the mt-genome of
M. leidyi
is the smallest animal mtDNA ever reported and is among the most derived. It has lost at least 25 genes, including
atp6
and all tRNA genes. We show that
atp6
has been relocated to the nuclear genome and has acquired introns and a mitochondrial targeting presequence, while tRNA genes have been genuinely lost, along with nuclear-encoded mt-aminoacyl tRNA synthetases. The mt-genome of
M. leidyi
also displays extremely high rates of sequence evolution, which likely led to the degeneration of both protein and rRNA genes. In particular, encoded rRNA molecules possess little similarity with their homologues in other organisms and have highly reduced secondary structures. At the same time, nuclear encoded mt-ribosomal proteins have undergone expansions, probably to compensate for the reductions in mt-rRNA. The unusual features identified in
M. leidyi
mtDNA make this organism an interesting system for the study of various aspects of mitochondrial biology, particularly protein and tRNA import and mt-ribosome structures, and add to its value as an emerging model species. Furthermore, the fast-evolving
M. leidyi
mtDNA should be a convenient molecular marker for species- and population-level studies.
The histone proteins have been probed by a variety of physical and chemical techniques in order to better characterize its various associations and states in solution. (1) The circular dichroism of ...freshly prepared chicken erythrocyte core histones were examined in high concentrations of ammonium sulfate and sodium chloride, conditions which cause drastic changes in the solubility and aggregative properties of these proteins. After sample clarification by ultracentrifugation, no significant net changes are detected in the secondary structure of the core histones in the range 2.0-2.5 M ammonium sulfate, nor is there any significant difference between these CD spectra and those obtained in 2 M NaCl. It was observed that sample clarification prior to taking CD spectra was necessary for signal stabilization, especially under conditions which begin to favor crystallization of the histones. (2) Mixtures of histones H3 and H4 were examined by analytical ultracentrifugation and CD to determine their association behavior and secondary structural content in high and low ionic strength solvents containing chloride, phosphate, or sulfate. H3 and H4 were also crosslinked using DSP to directly trap any molecular interactions occurring in solution. While H3 and H4 can, under certain conditions, exist as a dimer in solution, they behave as a stable (H3-H4)$\sb2$ tetramer under most conditions. This supports the concept of the core histone octamer having a tripartite organization rather than being composed of two heterotypic tetramers. (3) The energetics of interaction of H2A and H2B within the histone dimer and H3 and H4 within the histone tetramer over the ionic strength and pH ranges where the interaction of the dimer with the tetramer is particularly sensitive were examined using differential scanning calorimetry and circular dichroism. Changes in the enthalpies and secondary structure of the two systems correlate well with previous observations regarding the assembly of histone dimers and tetramers into the octamer complex and provide a thermodynamic basis for describing these phenomena.
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