Reiko Kikuno

Genome-wide Expression Analysis of Mouse Liver Reveals CLOCK-regulated Circadian Output Genes

CLOCK is a positive component of a transcription/translation-based negative feedback loop of the central circadian oscillator in the suprachiasmatic nucleus in mammals. To examine CLOCK-regulated circadian transcription in peripheral tissues, we performed microarray analyses using liver RNA isolated from Clock mutant mice. We also compared expression profiles with those of Cryptochromes (Cry1 and Cry2) double knockout mice. We identified more than 100 genes that fluctuated from day to night and of which expression levels were decreased in Clock mutant mice. In Cry-deficient mice, the expression levels of most CLOCK-regulated genes were elevated to the upper range of normal oscillation. Most of the screened genes had a CLOCK/BMAL1 binding site (E box) in the 5′-flanking region. We found that CLOCK was absolutely concerned with the circadian transcription of one type of liver genes (such as DBP, TEF, and Usp2) and partially with another (such as mPer1, mPer2, mDec1, Nocturnin, P450 oxidoreductase, and FKBP51) because the latter were damped but remained rhythmic in the mutant mice. Our results showed that CLOCK and CRY proteins are involved in the transcriptional regulation of many circadian output genes in the mouse liver. In addition to being a core component of the negative feedback loop that drives the circadian oscillator, CLOCK also appears to be involved in various physiological functions such as cell cycle, lipid metabolism, immune functions, and proteolysis in peripheral tissues.

Cloning and Crystal Structure of Hematopoietic Prostaglandin D Synthase

Hematopoietic prostaglandin (PG) D synthase is the key enzyme for production of the D and J series of prostanoids in the immune system and mast cells. We isolated a cDNA for the rat enzyme, crystallized the recombinant enzyme, and determined the three-dimensional structure of the enzyme complexed with glutathione at 2.3 A resolution. The enzyme is the first member of the sigma class glutathione S-transferase (GST) from vertebrates and possesses a prominent cleft as the active site, which is never seen among other members of the GST family. The unique 3-D architecture of the cleft leads to the putative substrate binding mode and its catalytic mechanism, responsible for the specific isomerization from PGH2 to PGD2.

HUGE: a database for human large proteins identified in the Kazusa cDNA sequencing project

HUGE is a database for human large proteins newly identified by Kazusa cDNA project, which aims to predict protein primary structures from sequences of human large cDNAs (>4 kb). In particular, cDNA clones capable of coding for large proteins (>50 kDa) are current targets of the project. More than 700 sequences of human cDNAs (average size, 5.1 kb) have been determined to date and deposited in the public databases. Notable information implied from the cDNAs and the predicted protein sequences can be obtained through HUGE via the World Wide Web at URL http://www.kazusa.or.jp/huge

Molecular Evolution of the Photolyase–Blue-Light Photoreceptor Family

Abstract. The photolyase–blue-light photoreceptor family is composed of cyclobutane pyrimidine dimer (CPD) photolyases, (6-4) photolyases, and blue-light photoreceptors. CPD photolyase and (6-4) photolyase are involved in photoreactivation for CPD and (6-4) photoproducts, respectively. CPD photolyase is classified into two subclasses, class I and II, based on amino acid sequence similarity. Blue-light photoreceptors are essential light detectors for the early development of plants. The amino acid sequence of the receptor is similar to those of the photolyases, although the receptor does not show the activity of photoreactivation. To investigate the functional divergence of the family, the amino acid sequences of the proteins were aligned. The alignment suggested that the recognition mechanisms of the cofactors and the substrate of class I CPD photolyases (class I photolyases) are different from those of class II CPD photolyases (class II photolyases). We reconstructed the phylogenetic trees based on the alignment by the NJ method and the ML method. The phylogenetic analysis suggested that the ancestral gene of the family had encoded CPD photolyase and that the gene duplication of the ancestral proteins had occurred at least eight times before the divergence between eubacteria and eukaryotes.

Close structural resemblance between putative polymerase of a Drosophila transposable genetic element 17.6 and pol gene product of Moloney murine leukaemia virus.

We have made a computer‐assisted search for homology among polymerases or putative polymerases of various viruses and a transposable element, the Drosophila copia‐like element 17.6. The search revealed that the putative polymerase (second open reading frame) of the copia‐like element 17.6 bears close resemblance in overall structural organization to the pol gene product of Moloney murine leukaemia virus (M‐MuLV): they show significant homology to each other at both the N‐ and C‐terminal portions, suggesting that the 17.6 putative polymerase carries two enzymatic activities, related to reverse transcriptase and DNA endonuclease. The putative polymerase of cauliflower mosaic virus (CaMV) shows striking homology with the putative polymerase of 17.6 over almost its entire length, but it lacks the DNA endonuclease‐related sequence. Furthermore, it was shown that the N‐terminal ends of the M‐MuLV pol product and the CaMV and 17.6 putative polymerases exhibit strong sequence homology with the gag‐specific protease (p15) of Rous sarcoma virus (RSV) as well as the amino acid sequence predicted from the gag/pol spacer sequence of human adult T‐cell leukaemia virus (HTLV). These p15‐related sequences contain a highly conserved stretch of amino acids which show a close similarity with sequences around the active site amino acids Asp‐Thr‐Gly of the acid protease family, suggesting that they have an activity similar to acid protease. On the basis of the alignment of reverse transcriptase‐related sequences, a dendrogram representing phylogenetic relationships among all the viruses compared together with 17.6 was constructed and its evolutionary implication is discussed.

HUGE: a database for human KIAA proteins, a 2004 update integrating HUGEppi and ROUGE

We have been developing a Human Unidentified Gene-Encoded (HUGE) protein database (http://www.kazusa.or.jp/huge) to summarize results from sequence analysis of human novel large (>4 kb) cDNAs identified in the Kazusa cDNA sequencing project. At present, HUGE contains 2031 cDNA entries (KIAA cDNAs), for each of which a gene/protein characteristic table has been prepared. Since we have been shifting our research attention from the identification and cloning of novel cDNAs to the functional analysis of the proteins encoded by these cDNAs (KIAA proteins), we have not substantially increased the number of cDNA entries in HUGE for some time. Instead, we have manually curated 451 KIAA cDNAs in order to prepare a set of genetic resources to facilitate the functional analysis of KIAA proteins. In addition, we have updated the contents of the corresponding gene/protein characteristic tables in HUGE and have constructed two subsidiary databases, HUGEppi (http://www. kazusa.or.jp/huge/ppi) and ROUGE (http://www. kazusa.or.jp/rouge), to make available the results from our study of KIAA protein function. HUGEppi shows detailed information on protein-protein interactions detected between 84 pairs of KIAA proteins by yeast two-hybrid screening. ROUGE summarizes the results of computer-assisted analyses of approximately 1000 mouse homologues of human large cDNAs that we identified.

Prediction of the Coding Sequences of Mouse Homologues of FLJ Genes: The Complete Nucleotide Sequences of 110 Mouse FLJ- Homologous cDNAs Identified by Screening of Terminal Sequences of cDNA Clones Randomly Sampled from Size-Fractionated Libraries

We have been conducting a human cDNA project to predict protein-coding sequences in long cDNAs (> 4 kb) since 1994. The number of these newly identified human genes exceeds 2000 and these genes are known as KIAA genes. As an extension of this project, we herein report characterization of cDNAs derived from mouse KIAA-homologous genes. A primary aim of this study was to prepare a set of mouse. KIAA-homologous cDNAs that could be used to analyze the physiological roles of KIAA genes in mice. In addition, comparison of the structures of mouse and human KIAA cDNAs might enable us to evaluate the integrity of KIAA cDNAs more convincingly. In this study, we selected mouse KIAA-homologous cDNA clones to be sequenced by screening a library of terminal sequences of mouse cDNAs in size-fractionated libraries. We present the entire sequences of 100 cDNA clones thus selected and predict their protein-coding sequences. The average size of the 100 cDNA sequences reached 5.1 kb and that of mouse KIAA-homologous proteins predicted from these cDNAs was 989 amino acid residues.

Exploration of Human ORFeome: High-Throughput Preparation of ORF Clones and Efficient Characterization of Their Protein Products

In this study, we established new systematic protocols for the preparation of cDNA clones, conventionally termed open reading frame (ORF) clones, suitable for characterization of their gene products by adopting a restriction-enzyme-assisted cloning method using the Flexi® cloning system. The system has following advantages: (1) preparation of ORF clones and their transfer into other vectors can be achieved efficiently and at lower cost; (2) the system provides a seamless connection to the versatile HaloTag® labeling system, in which a single fusion tag can be used for various proteomic analyses; and (3) the resultant ORF clones show higher expression levels both in vitro and in vivo. With this system, we prepared ORF clones encoding 1929 human genes and characterized the HaloTag-fusion proteins of its subset that are expressed in vitro or in mammalian cells. Results thus obtained have demonstrated that our Flexi® ORF clones are efficient for the production of HaloTag-fusion proteins that can provide a new versatile set for a variety of functional analyses of human genes.

Identification of three novel non-classical cadherin genes through comprehensive analysis of large cDNAs

The terminal sequences of long cDNAs from human brains were subjected to an improved method of motif-trap screening. This process resulted in the identification of three novel genes that encode proteins with 27, 27, and six cadherin domains that we denoted as KIAA1773, KIAA1774 and KIAA1775, respectively. Sequence analysis indicated that the products of these genes were non-classical cadherins. KIAA1773 was found to be a mammalian homologue of the Drosophila dachsous gene but the remaining two genes did not have any likely homologues in public databases. Assessment of their expression in rat tissues indicated that these genes are expressed in highly distinct and tissue-specific patterns. Notably, KIAA1775 is expressed almost exclusively in the olfactory bulb in the rat brain. In situ hybridization further showed that KIAA1775 is strongly expressed by the mitral and tufted cells in the main and accessory olfactory bulbs, suggesting that KIAA1775 may be important in the formation and maintenance of neuronal networks, particularly those in the olfactory bulb. This study clearly shows the importance and usefulness of our cDNA project in search for genes encoding large proteins, as this project has allowed us to identify several novel non-classical cadherin genes that have thus far not been detected by conventional methods.

Sequence homologies among mitochondrial DNA-coded URF2, URF4 and URF5

Mitochondrion URF Homology Gene duplication Evolution