The sequence of the human genome

Mitochondrial uncoupling proteins and phylogenesis--UCP4 as the ancestral uncoupling protein

We searched for the previously defined uncoupling protein (UCP) signatures [Jezek, P. and Urbánková, E. (2000) IUBMB Life 49, 63-70] in genomes of Drosophila melanogaster, Caenorhabditis elegans, Dictyostelium discoideum, and Arabidopsis thaliana. We identified four UCPs in Drosophila and one in Caenorhabditis or Dictyostelium as close relatives of human UCP4 (BMCP), but distant from UCP1, UCP2, UCP3, and two plant UCPs of Arabidopsis. But the third Arabidopsis UCP is the closest UCP4 relative. This suggests that UCP4 represents the ancestral UCP from which other mammalian and plant UCPs diverged. Speculations on UCP4 participation in apoptosis are thus supported by its early phylogenetic occurrence.

Goodbye to 'one by one' genetics

The completion of the Arabidopsis thaliana (mustard weed) genome sequence constitutes a major breakthrough in plant biology. It will revolutionize how we answer questions about the biology and evolution of plants as well as how we confront and resolve world-wide agricultural problems.

Sequence diversity in CYP3A promoters and characterization of the genetic basis of polymorphic CYP3A5 expression

Variation in the CYP3A enzymes, which act in drug metabolism, influences circulating steroid levels and responses to half of all oxidatively metabolized drugs. CYP3A activity is the sum activity of the family of CYP3A genes, including CYP3A5, which is polymorphically expressed at high levels in a minority of Americans of European descent and Europeans (hereafter collectively referred to as 'Caucasians'). Only people with at least one CYP3A5*1 allele express large amounts of CYP3A5. Our findings show that single-nucleotide polymorphisms (SNPs) in CYP3A5*3 and CYP3A5*6 that cause alternative splicing and protein truncation result in the absence of CYP3A5 from tissues of some people. CYP3A5 was more frequently expressed in livers of African Americans (60%) than in those of Caucasians (33%). Because CYP3A5 represents at least 50% of the total hepatic CYP3A content in people polymorphically expressing CYP3A5, CYP3A5 may be the most important genetic contributor to interindividual and interracial differences in CYP3A-dependent drug clearance and in responses to many medicines.

Emerging technologies in yeast genomics

The genomic revolution is undeniable: in the past year alone, the term 'genomics' was found in nearly 500 research articles, and at least 6 journals are devoted solely to genomic biology. More than just a buzzword, molecular biology has genuinely embraced genomics (the systematic, large-scale study of genomes and their functions). With its facile genetics, the budding yeast Saccharomyces cerevisiae has emerged as an important model organism in the development of many current genomic methodologies. These techniques have greatly influenced the manner in which biology is studied in yeast and in other organisms. In this review, we summarize the most promising technologies in yeast genomics.

Predicting the functional consequences of non-synonymous single nucleotide polymorphisms: structure-based assessment of amino acid variation

We have developed a formalism and a computational method for analyzing the potential functional consequences of non-synonymous single nucleotide polymorphisms. Our approach uses a structural model and phylogenetic information to derive a selection of structure and sequence-based features serving as indicators of an amino acid polymorphim's effect on function. The feature values can be integrated into a probabilistic assessment of whether an amino acid polymorphism will affect the function or stability of a target protein. The method has been validated with data sets of unbiased mutations in the lac repressor and lysoyzyme. Applying our methodology to recent surveys of genetic variation in the coding regions of clinically important genes, we estimate that approximately 26-32 % of the natural non-synonymous single nucleotide polymorphisms have effects on function. This estimate suggests that a typical person will have about 6240-12,800 heterozygous loci that encode proteins with functional variation due to natural amino acid polymorphism.

Computational genomics

We now know how to read the sequences of nucleotide letters that comprise the genome at a rather frightening speed--a several-million-base bacterial genome in several days is not a problem for one of the sequencing centers, and a billion-base eukaryotic genome can be done in less than a year. But reading a text and understanding it are two different things. So how well can we understand the genome sequences? The answer to this question is central to the whole enterprise of genomics, and this is where computational analysis of genomes takes the driver's seat. Here I will try to briefly outline some major goals, problems, challenges and approaches of computational genomics. Such a young field is already quite diverse, and in this short article I will concentrate on several issues that seen to be critical for deciphering biology from genome sequences, rather than mathematical and computer-science aspects that are well covered in several excellent books.

Infectious diseases: considerations for the 21st century

The discipline of infectious diseases will assume added prominence in the 21st century in both developed and developing nations. To an unprecedented extent, issues related to infectious diseases in the context of global health are on the agendas of world leaders, health policymakers, and philanthropies. This attention has focused both on scientific challenges such as vaccine development and on the deleterious effects of infectious diseases on economic development and political stability. Interest in global health has led to increasing levels of financial support, which, combined with recent technological advances, provide extraordinary opportunities for infectious disease research in the 21st century. The sequencing of human and microbial genomes and advances in functional genomics will underpin significant progress in many areas, including understanding human predisposition and susceptibility to disease, microbial pathogenesis, and the development new diagnostics, vaccines, and therapies. Increasingly, infectious disease research will be linked to the development of the medical infrastructure and training needed in developing countries to translate scientific advances into operational reality.

A high-resolution radiation hybrid map of the human genome draft sequence

We have constructed a physical map of the human genome by using a panel of 90 whole-genome radiation hybrids (the TNG panel) in conjunction with 40,322 sequence-tagged sites (STSs) derived from random genomic sequences as well as expressed sequences. Of 36,678 STSs on the TNG radiation hybrid map, only 3604 (9.8%) were absent from the unassembled draft sequence of the human genome. Of 20,030 STSs ordered on the TNG map as well as the assembled human genome draft sequence and the Celera assembled human genome sequence, 36% of the STSs had a discrepant order between the working draft sequence and the Celera sequence. The TNG map order was identical to one of the two sequence orders in 60% of these discrepant cases.

Computational comparison of two draft sequences of the human genome

We are in the enviable position of having two distinct drafts of the human genome sequence. Although gaps, errors, redundancy and incomplete annotation mean that individually each falls short of the ideal, many of these problems can be assessed by comparison. Here we present some comparative analyses of these drafts. We look at a number of features of the sequences, including sequence gaps, continuity, consistency between the two sequences and patterns of DNA-binding protein motifs.

Initial sequencing and analysis of the human genome

The human genome holds an extraordinary trove of information about human development, physiology, medicine and evolution. Here we report the results of an international collaboration to produce and make freely available a draft sequence of the human genome. We also present an initial analysis of the data, describing some of the insights that can be gleaned from the sequence.

The olfactory receptor family album

Analysis of the human genome draft sequences has revealed a more complete portrait of the olfactory receptor gene repertoire in humans than was available previously. The new information provides a basis for deeper analysis of the functions of the receptors, and promises new insights into the evolutionary history of the family.

Endogenous retroviruses in the human genome sequence

The human genome contains many endogenous retroviral sequences, and these have been suggested to play important roles in a number of physiological and pathological processes. Can the draft human genome sequences help us to define the role of these elements more closely?

Fully Automated Parallel Oligonucleotide Synthesizer

Design and construction of automated synthesizers using the tilted plate centrifugation technology is described. Wash solutions and reagents common to all synthesized species are delivered automatically through a 96-channel distributor connected to a gear pump through two four-port selector valves. Building blocks and other specific reagents are delivered automatically through banks of solenoid valves, positioned over the individual wells of the microtiterplate. These instruments have the following capabilities: Parallel solid-phase oligonucleotide synthesis in the wells of polypropylene microtiter plates, which are slightly tilted down towards the center of rotation, thus generating a pocket in each well, in which the solid support is collected during centrifugation, while the liquid is expelled from the wells. Eight microtiterplates are processed simultaneously, providing thus a synthesizer with a capacity of 768 parallel syntheses. The instruments are capable of unattended continuous operation, providing thus a capacity of over two millions 20-mer oligonucleotides in a year.

Loss of N-glycolylneuraminic acid in humans: Mechanisms, consequences, and implications for hominid evolution

The surface of all mammalian cells is covered with a dense and complex array of sugar chains, which are frequently terminated by members of a family of molecules called sialic acids. One particular sialic acid called N-glycolylneuraminic acid (Neu5Gc) is widely expressed on most mammalian tissues, but is not easily detectable on human cells. In fact, it provokes an immune response in adult humans. The human deficiency of Neu5Gc is explained by an inactivating mutation in the gene encoding CMP-N-acetylneuraminic acid hydroxylase, the rate-limiting enzyme in generating Neu5Gc in cells of other mammals. This deficiency also results in an excess of the precursor sialic acid N-acetylneuraminic acid (Neu5Ac) in humans. This mutation appears universal to modern humans, occurred sometime after our last common ancestor with the great apes, and happens to be one of the first known human-great ape genetic differences with an obvious biochemical readout. While the original selection mechanisms and major biological consequences of this human-specific mutation remain uncertain, several interesting clues are currently being pursued. First, there is evidence that the human condition can explain differences in susceptibility or resistance to certain microbial pathogens. Second, the functions of some endogenous receptors for sialic acids in the immune system may be altered by this difference. Third, despite the lack of any obvious alternate pathway for synthesis, Neu5Gc has been reported in human tumors and possibly in human fetal tissues, and traces have even been detected in normal human tissues. One possible explanation is that this represents accumulation of Neu5Gc from dietary sources of animal origin. Finally, a markedly reduced expression of hydroxylase in the brains of other mammals raises the possibility that the human-specific mutation of this enzyme could have played a role in human brain evolution.

Abundant protein domains occur in proportion to proteome size

BACKGROUND

Conserved domains in proteins have crucial roles in protein interactions, DNA binding, enzyme activity and other important cellular processes. It will be of interest to determine the proportions of genes containing such domains in the proteomes of different eukaryotes.

RESULTS

The average proportion of conserved domains in each of five eukaryote genomes was calculated. In pairwise genome comparisons, the ratio of genes containing a given conserved domain in the two genomes on average reflected the ratio of the predicted total gene numbers of the two genomes. These ratios have been verified using a repository of databases and one of its subdivisions of conserved domains.

CONCLUSIONS

Many conserved domains occur as a constant proportion of proteome size across the five sequenced eukaryotic genomes. This raises the possibility that this proportion is maintained because of functional constraints on interacting domains. The universality of the ratio in the five eukaryotic genomes attests to its potential importance.

What use is the human genome for understanding the mouse?

Having a working draft of the human genome sequence is proving invaluable to mouse genetic and genomic studies, providing a useful stepping-stone towards the finished sequence of the mouse genome.

Characterizing glycosylation pathways

Numerous factors that influence cell-surface carbohydrate composition remain to be elucidated. The combination of novel biochemical and metabolism-based approaches with emerging genomic methods promises to accelerate efforts to understand glycosylation.

The human olfactory receptor repertoire

BACKGROUND

The mammalian olfactory apparatus is able to recognize and distinguish thousands of structurally diverse volatile chemicals. This chemosensory function is mediated by a very large family of seven-transmembrane olfactory (odorant) receptors encoded by approximately 1,000 genes, the majority of which are believed to be pseudogenes in humans.

RESULTS

The strategy of our sequence database mining for full-length, functional candidate odorant receptor genes was based on the high overall sequence similarity and presence of a number of conserved sequence motifs in all known mammalian odorant receptors as well as the absence of introns in their coding sequences. We report here the identification and physical cloning of 347 putative human full-length odorant receptor genes. Comparative sequence analysis of the predicted gene products allowed us to identify and define a number of consensus sequence motifs and structural features of this vast family of receptors. A new nomenclature for human odorant receptors based on their chromosomal localization and phylogenetic analysis is proposed. We believe that these sequences represent the essentially complete repertoire of functional human odorant receptors.

CONCLUSIONS

The identification and cloning of all functional human odorant receptor genes is an important initial step in understanding receptor-ligand specificity and combinatorial encoding of odorant stimuli in human olfaction.