Agents that target telomerase and telomeres

Telomeres are guanine-rich regions that are located at the ends of chromosomes and are essential for preventing aberrant recombination and protecting against exonucleolytic DNA degradation. Telomeres are maintained by telomerase, an RNA-dependent DNA polymerase. Because telomerase is known to be expressed in tumor cells, which concurrently have short telomeres, and not in most somatic cells, which usually have long telomeres, telomerase and telomere structures have been recently proposed as attractive targets for the discovery of new anticancer agents. The most exciting current strategies are aimed at specifically designing new drugs that target telomerase or telomeres and new models have been formulated to study the biological effects of inhibitors of telomerase and telomeres both in vitro and in vivo.     

Origin, evolution, and excision of internal eliminated segments in germline genes of ciliates

Three hypotheses on the evolutionary/molecular origin of internal eliminated segments (IESs) in the germline of hypotrichous ciliates are discussed in the context of the high rate of mutation accumulation in IESs, shifting of IESs during speciation, and evolutionary scrambling of segments within some hypotrich germline genes. Developmental excision of IESs from the germline in Paramecium suggests that the parental macronucleus may provide nucleic acid sequence information to guide excision of IESs and splicing of macronuclear-destined sequences. In ciliates of the oxytrichid/stylonychid group, such a mechanism could explain the precision of excision of IESs and gene unscrambling. Recently initiated molecular/genetic studies may eventually clarify the role of the parental macronucleus in IES excision and gene unscrambling as well as the molecular mechanisms of these events.     

Artificial dinuclear phosphoesterases

Many elegant dinuclear transition metal and lathanide complexes that efficiently hydrolyze phosphate esters including RNA and DNA have been reported recently. In most cases, the dinuclear complexes are much more reactive than the corresponding mononuclear metal complexes. Furthermore, structural and kinetic data indicate that substantial rate acceleration for phosphate diester cleavage is obtained by bridging the dinuclear metal centers with the two phosphoryl oxygens. Interestingly, such bridging structures have recently been implicated in several metalloenzyme catalyzed phosphate hydrolyses.     

Innovative approaches to novel antibacterial drug discovery

Increasing antibiotic resistance in microorganisms and new emerging pathogens have become a major problem in our society. Rising to satisfy this urgent medical need is a recent confluence of powerful new drug discovery technologies: combinatorial chemistry; sequence and functional genomic analysis; and novel methods of high-throughput screening. The combination of these technologies will bring to bear untapped power in the search for new antimicrobials.     

Bacterial genome sequencing and drug discovery

The availability of bacterial genome sequence information has opened up many new strategies for antibacterial drug hunting. There are obvious benefits for the idetification and evaluation of new drug targets, but genomic-based technology is also beginning to provide new tools for the downstream, preclinical, optimisation of compounds. The greatest benefit from these new approaches lies in the ability to examine the entire genome (or several genomes) simultaneously and in total. In this way, one potential target can be evaluated against another, and either the total effects of functional impairment can be established or the effects of a compound can be compared across species.     

The mycobacterial cell wall: structure, biosynthesis and sites of drug action

Structural analysis has been successfully implemented recently to obtain valuable information on the mycobacterial cell wall components, many of which have formed the basis for biosynthesis and functional studies towards developing better drugs and possible vaccines. The highly complex and well organized structure unique to mycobacteria, represents the best target for novel antimycobacterial agents. Until recently, our knowledge of the enzymes responsible for the biogenesis of the cell wall components was almost negligible. The pathways are now being elucidated in several laboratories. Highlights of this review include significant advances in the structure and biochemistry of the major cell wall components and potenital targets for generation of new drugs.     

Post-translational modification of proteins and the discovery of new medicine

Post-translational modifications are fundamental to processes controlling behaviour, including cellular signaling, growth and transformation. As the molecular basis of protein modifications in normal and disease processes are becoming better defined, so new strategies for designing therapeutic entities to control complex disease processes are emerging.     

Liver stem cells: a two compartment system

Hepatocytes and biliary epithelia are phenotypically very dissimilar, but share a common ancestry. Hepatocytes regenerate very efficiently, and their division potential indicates that many of them are functional stem cells. When hepatocyte-damaging agents also impair the regenerative ability of surviving hepatocytes, a potential stem cell system of biliary origin is activated to generate new hepatocytes — a reversal of ontogeny. Now both bile duct derived cells and hepatocytes can be isolated from the liver, genetically modified in vitro and returned to their in vivo origins where, after considerable population expansion, they can function as hepatocytes — paving the way for ex vivo gene therapy.     

Protein—drug complexes important for immunoregulation and organ transplantation

Recently, two structures of the Ser/Thr phosphorylase calcineurin in complex with FK506 and its cognate immunophilin, FKBP12, have been reported, both solved by small pharmaceutical companies focused on structure-based drug design. A realization, however, that the toxicities associated with calcineurin-mediated immunosuppressants might be mechanism based has driven the current interest in alternative approaches to autoimmunity prophylaxis and preventing transplant rejection. Regulatory approval in 1995 of the immunosuppressant prodrug mycophenolate mofetil, whose active metabolite, mycophenolic acid, inhibits inosine monophosphate dehydrogenase, has focused attention on the potential significance of the de novo purine-biosynthesis pathway as a target for immunosuppressive drugs, leading ultimately to the solution of enzyme structure as a drug design target. As this and other clinically relevant targets are discovered, elaborated and refined via the activity of their cognate agents (as was the case for the phosphatase calcineurin via the activity of cyclosporin), a critical opportunity should ensue for structural biology to exert a profound effect on the future development of these therapies.     

Virus-like particles as vaccines and vessels for the delivery of small molecules

Virus-like particles (VLPs) structurally mimic the viral capsid and have therefore been extensively, and quite successfully, used as vaccine and viral serology reagents. The ability of VLPs to include nucleic acids and small molecules has also made them novel vessels for gene and drug delivery. The regular, repetitive surface of VLPs has been exploited as a template for nanoscale synthesis. Recent progress has been made in the development of several virus models.     

The evolution of the Hox cluster: insights from outgroups

Two burgeoning research trends are helping to reconstruct the evolution of the Hox cluster with greater detail and clarity. First, Hox genes are being studied in a broader phylogenetic sampling of taxa: the past year has witnessed important new data from teleost fishes, onychophorans, myriapods, polychaetes, glossiphoniid leeches, ribbon worms, and sea anemones. Second, commonly accepted notions of animal relationships are being challenged by alternative phylogenetic hypotheses that are causing us to rethink the evolutionary relationships of important metazoan lineages, especially arthropods, annelids, nematodes, and platyhelminthes.     

In vivo clearance of Japanese encephalitis virus by adoptively transferred virus specific cytotoxic T lymphocytes

Japanese encephalitis virus (JEV) is a positive stranded RNA virus that belongs to the flavivirus group. JEV infection damages the central nervous system (CNS) and is one of the main causative agents of acute encephalitis. H-2 restricted virus-specific cytotoxic T lymphocytes (CTL) have been generated specifically against JEV in our laboratory and these CTL have been shown to protect mice against lethal challenge with JEV. Virus replication was found to be inhibited in the brains of animals that were adoptively transferred with JEV specific CTL as revealed by immunohistological staining as well as viral plaque assays. We further show that virus specific CTL could be recovered from such protected mice as long as 45 days after adoptive transfer.     

Everything in moderation: Archaea as ‘non-extremophiles’

Well characterized and cultivated archaea are prokaryotic specialists that thrive in habitats of elevated temperature, low pH, high salinity, or strict anoxia. Recently, however, new groups of abundant, uncultivated archaea have been found to be widespread in more pedestrian biotopes, including marine plankton, terrestrial soils, lakes, marine and freshwater sediments, and in association with metazoa. Research efforts are presently focused on characterizing the physiology, biochemistry and genetics of these abundant and cosmopolitan but poorly understood archaea.     

S-phase and DNA-damage checkpoints: a tale of two yeasts

Many genes required for the S-phase and DNA-damage checkpoints have been identified in the yeasts Saccharomyces cerevisiae and Schizosaccharomyces pombe. This year many checkpoint genes have been sequenced, providing new information about the mechanism of checkpoint control. Several of these genes are conserved between the two yeasts but others are species-specific.     

The chemical-biological interface: developments in automated and miniaturised screening technology

The rapidly changing developments in genomics and combinatorial chemistry, generating new drug targets and large numbers of compounds, have caused a revolution in high-throughput screening technologies. Key to this revolution has been the introduction of robotics and automation, together with new biological assay technologies (e.g., homogeneous time resolved fluorescence). With ever increasing workloads, together with economic and logistical constraints, miniaturisation is rapidly becoming essential for the future of high-throughput screening and combinatorial chemistry. This is evident from the introduction of high-density microtitre plates, small volume liquid handling robots and associated detection technology.     

Will combinatorial chemistry deliver real medicines?

Over the next decade, the impact of library synthesis will play a major role in shortening the lead optimization phase of drug discovery. The prognosis for combinatorial chemistry to discover fundamentally different new classes of therapeutically active small molecules against some of the more difficult biological targets is less certain. Expectations are high because the technology potentially allows us to sample available drug space by synthesizing all possible small molecule ligands (variously estimated to be between 10³⁰–10⁵⁰ compounds). Some caution is advised, however, since, despite recent increases in high-throughput screening of substantially greater numbers of synthetic compounds and natural products, we are not routinely finding a plethora of new structures. The outcome may be that combinatorial chemistry offers us the ability to work faster on finding ligands for well-established tractable targets, such as G-protein-coupled receptors, ion channels or proteases, rather than, say, the more complex protein—protein interactions which from the majority of targets in signal transduction pathways.     

Functional role of plateau potentials in vertebrate motor neurons

The expression of plateau potentials in spinal motor neurons is regulated by neuromodulatory substances. Recent experiments have shed new light on this regulation at the cellular level. It is now possible to evaluate the existence of plateau potentials in intact organisms, including humans, and to address the functional role of plateau potentials in motor control, as well as in information transfer in the brain.     

Metazoan phylogenies: falling into place or falling to pieces? A palaeontological perspective

Metazoan phylogeny is in a state of ferment, stirred by the addition of new molecular trees as well as controversial interpretations of molecular ‘clocks’. Concerning the latter topic, the clocks recurrently point to divergence times substantially older than the known fossil record. Some attempt reconciliation by appealing to a conveniently cryptic interval prior to the first fossils. This effectively reduces the fossil record to an erratic search-light giving only glimpses into the true evolutionary history. Other options, however, remain open. Molecular clocks may themselves run erratically and what happens in molecular history may not coincide with the emergence of body plans.     

Will genetics really revolutionize the drug discovery process?

Genetics has played only a modest role in drug discovery, but new technologies will radically change this. Whole genome sequencing will identify new drug discovery targets, and emerging methods for the determination of gene function will increase the ability to select robust targets. Detection of single nucleotide polymorphisms and common polymorphisms will enhance the investigation of polygenic diseases and the use of genetics in drug development. Oligonucleotide arraying technologies will allow analysis of gene expression patterns in novel ways.     

Biorobotic approaches to the study of motor systems

Biorobotics is a promising new area of research at the interface between biology and robotics. Robots can either be used as physical models of biological systems or be directly inspired by biological studies. A great deal of progress has recently been made in biorobotic studies of locomotion, orientation, and vertebrate arm control.