CENP-50 is required for papilloma development in the two-stage skin carcinogenesis model.

CENP-50/U is a component of the CENP-O complex (CENP-O/P/Q/R/U) and localizes to the centromere throughout the cell cycle. Aberrant expression of CENP-50/U has been reported in many types of cancers. However, as Cenp-50/U-deficient mice die during early embryogenesis, its functions remain poorly understood in vivo. To investigate the role of Cenp-50/U in skin carcinogenesis, we generated Cenp-50/U conditional knockout (K14CreER -Cenp-50/Ufl/fl ) mice and subjected them to the 7,12-dimethylbenz(a)anthracene (DMBA)/terephthalic acid (TPA) chemical carcinogenesis protocol. As a result, early-stage papillomas decreased in Cenp-50/U-deficient mice. In contrast, Cenp-50/U-deficient mice demonstrated almost the same carcinoma incidence as control mice. Furthermore, mRNA expression analysis using DMBA/TPA-induced papillomas and carcinomas revealed that Cenp-50/U expression levels in papillomas were significantly higher than in carcinomas. These results suggest that Cenp-50/U functions mainly in early papilloma development and it has little effect on malignant conversion.

CENP-R acts bilaterally as a tumor suppressor and as an oncogene in the two-stage skin carcinogenesis model.

CENP-R is a component of the CENP-O complex, including CENP-O, CENP-P, CENP-Q, CENP-R, and CENP-U and is constitutively localized to kinetochores throughout the cell cycle in vertebrates. CENP-R-deficient chicken DT40 cells are viable and show a very minor effect on mitosis. To investigate the functional roles of CENP-R in vivo, we generated CENP-R-deficient mice (Cenp-r-/- ). Mice heterozygous or homozygous for Cenp-r null mutation are viable and healthy, with no apparent defect in growth and morphology, indicating Cenp-r is not essential for normal development. Accordingly, to investigate the role of the Cenp-r gene in skin carcinogenesis, we subjected Cenp-r-/- mice to the 7,12-dimethylbenz(a)anthracene (DMBA)/TPA chemical carcinogenesis protocol and monitored tumor development. As a result, Cenp-r-/- mice initially developed significantly more papillomas than control wild-type mice. However, papillomas in Cenp-r-/- mice showed a decrease of proliferative cells and an increase of apoptotic cells. As a result, they did not grow bigger and some papillomas showed substantial regression. Furthermore, papillomas in Cenp-r-/- mice showed lower frequency of malignant conversion to squamous cell carcinomas. These results indicate Cenp-r functions bilaterally in cancer development: during early developmental stages, Cenp-r functions as a tumor suppressor, but during the expansion and progression of papillomas it functions as a tumor-promoting factor.

Constitutive centromere-associated network controls centromere drift in vertebrate cells.

Centromeres are specified by sequence-independent epigenetic mechanisms, and the centromere position may drift at each cell cycle, but once this position is specified, it may not be frequently moved. Currently, it is unclear whether the centromere position is stable. To address this question, we systematically analyzed the position of nonrepetitive centromeres in 21 independent clones isolated from a laboratory stock of chicken DT40 cells using chromatin immunoprecipitation combined with massive parallel sequencing analysis with anti-CENP-A antibody. We demonstrated that the centromere position varies among the clones, suggesting that centromere drift occurs during cell proliferation. However, when we analyzed this position in the subclones obtained from one isolated clone, the position was found to be relatively stable. Interestingly, the centromere drift was shown to occur frequently in CENP-U- and CENP-S-deficient cells. Based on these results, we suggest that the centromere position can change after many cell divisions, but this drift is suppressed in short-term cultures, and the complete centromere structure contributes to the suppression of the centromere drift.

The CENP-O complex requirement varies among different cell types.

CENP-U (CENP-50) is a component of the CENP-O complex, which includes CENP-O, CENP-P, CENP-Q, CENP-R, and CENP-U and is constitutively localized at kinetochores throughout the cell cycle in vertebrates. Although CENP-U deficiency results in some mitotic defects in chicken DT40 cells, CENP-U-deficient chicken DT40 cells are viable. To examine the functional roles of CENP-U in an organism-dependent context, we generated CENP-U-deficient mice. The CENP-U-deficient mice died during early embryogenesis (approximately E7.5). Thus, conditional CENP-U-deficient mouse ES cells were generated to analyze CENP-U-deficient phenotypes at the cell level. When CENP-U was disrupted in the mouse ES cells, all CENP-O complex proteins disappeared from kinetochores. In contrast, other kinetochore proteins were recruited in CENP-U-deficient mouse ES cells as CENP-U-deficient DT40 cells. However, the CENP-U-deficient ES cells died after exhibiting abnormal mitotic behavior. Although CENP-U was essential for cell viability during mouse early embryogenesis, CENP-U-deficient mouse embryonic fibroblast cells were viable, similar to the DT40 cells. Thus, although both DT40 and ES cells with CENP-U deficiency have similar mitotic defects, cellular responses to mitotic defects vary among different cell types.

Human protein factory for converting the transcriptome into an in vitro-expressed proteome,.

Appropriate resources and expression technology necessary for human proteomics on a whole-proteome scale are being developed. We prepared a foundation for simple and efficient production of human proteins using the versatile Gateway vector system. We generated 33,275 human Gateway entry clones for protein synthesis, developed mRNA expression protocols for them and improved the wheat germ cell-free protein synthesis system. We applied this protein expression system to the in vitro expression of 13,364 human proteins and assessed their biological activity in two functional categories. Of the 75 tested phosphatases, 58 (77%) showed biological activity. Several cytokines containing disulfide bonds were produced in an active form in a nonreducing wheat germ cell-free expression system. We also manufactured protein microarrays by direct printing of unpurified in vitro-synthesized proteins and demonstrated their utility. Our 'human protein factory' infrastructure includes the resources and expression technology for in vitro proteome research.

A novel high-throughput (HTP) cloning strategy for site-directed designed chimeragenesis and mutation using the Gateway cloning system.

There is an increasing demand for easy, high-throughput (HTP) methods for protein engineering to support advances in the development of structural biology, bioinformatics and drug design. Here, we describe an N- and C-terminal cloning method utilizing Gateway cloning technology that we have adopted for chimeric and mutant genes production as well as domain shuffling. This method involves only three steps: PCR, in vitro recombination and transformation. All three processes consist of simple handling, mixing and incubation steps. We have characterized this novel HTP method on 96 targets with >90% success. Here, we also discuss an N- and C-terminal cloning method for domain shuffling and a combination of mutation and chimeragenesis with two types of plasmid vectors.