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SummaryIn this study, we investigated the costimulatory activity of L-selectin in primary mouse T cells. Proliferation induced by immobilized anti-CD3 antibody was enhanced by immobilized anti-L-selectin antibody. In contrast to the anti-CD28 antibody, anti-L-selectin antibody did not enhance interleukin-2 (IL-2) expression. One of the cyclin-dependent kinase (cdk) inhibitors, p27, was reduced by costimulation with anti-L-selectin antibody, as with anti-CD28 antibody, suggesting that the enhancement of T-cell proliferation is the result of a reduced p27 level. Since anti-L-selectin antibody enhanced the activation of extracellular signal-regulated protein kinase (ERK) induced by anti-CD3 antibody, ERK plays an important role in signal integration during costimulation. These results suggest that the mechanism of T-cell costimulation is at least partially different between CD28 and L-selectin, although the two mechanisms share a common downstream event, a reduction of p27 level, as a critical biochemical event in the cell cycle progression of T cells.

Here we report the methylation status of the chicken ovalbumin promoter. Genomic DNA of oviduct from immature chickens and laying hens was analyzed through bisulfite genomic sequencing. In the ovalbumin control locus up to the 6 kb upstream region, CpG sites were methylated in immature chickens, except for several sites, and almost all CpGs residing in DNase I hypersensitive sites I, II, and III, but not IV, were selectively unmethylated in ovalbumin expressing chickens. Chromatin immunoprecipitation assays showed that the ovalbumin control region was associated with acetylated histone H3 but not with dimethylated histone H3 at Lys 27. These results demonstrate that DNA demethylation was restricted to short DNA regions of DNase I hypersensitive sites, especially to those which participated in estrogen-responsiveness, even when cells expressed extremely high levels of ovalbumin and these sites were associated with acetylated histones.

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