It has been reported that CUG, a universal leucine codon, is read as serine in an asporogenic yeast, Candida cylindracea. The distribution of this non-universal genetic code in various yeast species was studied using an in vitro translation assay system with a synthetic messenger RNA containing CUG codons in-frame. It was found that CUG is used as a serine codon in six out of the fourteen species examined, while it is used for leucine in the remaining eight. The tRNA species responsible for the translation of codon CUG as serine was detected in all the six species in which CUG is translated as serine. The grouping according to the CUG codon assignments in these yeast species shows a good correlation with physiological classification by the chain lengths of the isoprenoid moiety of ubiquinone and the cell-wall sugar contained in the yeasts. The six Candida species examined in which CUG is used as serine belong to one distinct group in Hemiascomycetes.

MicroRNAs (miRNAs) are endogenous non-coding small RNAs that can regulate the expression of complementary mRNA targets. Identifying tissue-specific miRNAs is the first step toward understanding the biological functions of miRNAs, which include the regulation of tissue differentiation and the maintenance of tissue identity. In this study, we performed small RNA library sequencing in adult mouse testis and ovary to reveal their characteristic organ-and gender-specific profiles and to elucidate the characteristics of the miRNAs expressed in the reproductive system. We obtained 10 852 and 11 744 small RNA clones from mouse testis and ovary respectively (greater than 10 000 clones per organ), which included 6630 (159 genes) and 10 192 (154 genes) known miRNAs. A high level of efficiency of miRNA library sequencing was achieved: 61% (6630 miRNA clones/10 852 small RNA clones) and 87% (10 192/11 744) for adult mouse testis and ovary respectively. We obtained characteristic miRNA signatures in testis and ovary; 55 miRNAs were detected highly, exclusively, or predominantly in adult mouse testis and ovary, and discovered two novel miRNAs. Male-biased expression of miRNAs occurred on the X-chromosome. Our data provide important information on sex differences in miRNA expression that should facilitate studies of the reproductive organ-specific roles of miRNAs. Reproduction (2008) 136 811-822

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SKP2, an F-box protein constituting the substrate recognition subunit of the SCF(SKP2) ubiquitin ligase complex, is implicated in ubiquitin-mediated degradation of the cyclin-dependent kinase inhibitor p27(KIP1). Our earlier studies revealed SKP2 as a target gene within the 5p13 amplicon that is often seen in small-cell lung cancers. In the present study we examined amplification status and expression levels of SKP2 in non-small-cell lung cancer (NSCLC) and investigated its clinicopathological significance in this type of tumor because amplification of DNA at 5p13 is observed frequently in NSCLCs as well as in small-cell lung cancers. SKP2 exhibited amplification in 5 (20%) of 25 cell lines derived from NSCLC, and the transcript was overexpressed in 11 (44%) of the 25 lines. Moreover, expression of SKP2 was up-regulated significantly in 60 primary NSCLC tumors as compared to nontumorous lung tissues (P < 0.0001). Elevated expression of SKP2 correlated significantly with positive lymph node metastasis (P = 0.007), with stage II or higher of the international TNM classification (P = 0.014), with poor or moderate differentiation (P < 0.001), and with the presence of squamous cell carcinoma (P = 0.037). Reduction of SKP2 expression by transfection of an anti-sense oligonucleotide inhibited invasion and migration of NSCLC cells in culture. Our results suggest that SKP2 may be involved in progression of NSCLC, and that targeting this molecule could represent a promising therapeutic option.

Prospermatogonia, or gonocytes, are the cells that differentiate from primordial germ cells to the first mature type of spermatogonia in the developing testis. Although prospermatogonia play a central role in this stage (i.e., prespermatogenesis), the details regarding their characterization have not been fully elucidated. Recently, we identified a novel mouse testicular germ cell-specific antigen, TES101 reactive protein (TES101RP), in the adult mouse testis. The protein TES101RP is also designated as protein TEX101. In the present study, we investigated the expression of TEX101 on germ cells in developing mouse gonads using histochemical techniques (i.e., immunohistochemistry, BrdU labeling, and TUNEL staining) and reverse transcription-polymerase chain reaction. TEX101 appeared on germ cells in both male and female gonads after the pregonadal period. In the testis, TEX101 was expressed constitutively on surviving prospermatogonia during prespermatogenesis. After the initiation of spermatogenesis, the prospermatogonia differentiated into spermatogonia. TEX101 expression disappeared from the spermatogonia, but reappeared on spermatocytes and spermatids. In the ovary, TEX101 was expressed on germ cells until the start of folliculogenesis; TEX101 was not detected on oocytes that were surrounded by follicular cells. These findings indicate that TEX101 is a specific marker for both male and female germ cells during gonadal development. Because the on and off switching of TEX101 expression in germ cells almost parallels the kinetics of gametogenesis, TEX101 may play an important physiological role in germ cell development.