Young-Ju Lee

Comprehensive analysis of microRNA-mRNA co-expression in circadian rhythm.

To investigate the potential role of microRNA (miRNA) in the regulation of circadian rhythm, we performed microarray-based expression profiling study of both miRNA and mRNA in mouse liver for 48 h at 4-hour intervals. Circadian miRNA-mRNA target pair is defined as the pair both elements of which show circadian expression patterns and the sequence-based target relationship of which can be predicted. Circadian initiators, Clock and Bmal1, showed inversely correlated circadian expression patterns against their corresponding miRNAs, miR-181d and miR-191, targeting them. In contrast, circadian suppressors, Per, Cry, CKIe and Rev-erba, exhibited positively correlated circadian expression patterns to their corresponding miRNAs. Genomic location analysis revealed that intronic region showed higher abundance of cyclic than non-cyclic miRNAs targeting circadian genes while other (i.e., 3-UTR, exon and intergenic) regions showed no difference. It is suggested that miRNAs are involved in the regulation of peripheral circadian rhythm in mouse liver by modulating Clock:Bmal1 complex. Identifying specific miRNAs and their targets that are critically involved in circadian rhythm will provide a better understanding of the regulation of circadian-clock system.

A dominant mesomelic dysplasia associated with a 1.0-Mb microduplication of HOXD gene cluster at 2q31.1

A three-generation family with four patients affected by a novel mesomelic dysplasia was investigated for genome-wide DNA copy number variation profiles. This revealed a microduplication of a 1.0-Mb chromosomal segment at 2q31.1 spanning nine Homeo box D (HOXD) genes that co-segregated with the phenotype. Quantitative PCR analysis of a gene within this duplicated region showed consistent results. Mesomelic dysplasia Kantaputra type (MDK; MIM 156232),which shares some phenotypes with this family, has also been mapped to a chromosomal region comprising 2q31.1, raising the possibility that MDK and the condition observed in this family may be allelic.

Highly enantioselective synthesis of 5-phenyl-2-alkylprolines using phase-transfer catalytic alkylation

An efficient enantioselective synthetic method for the synthesis of (2R)-5-phenyl-2-alkylproline tert-butyl esters was reported. The phase-transfer catalytic alkylation of tert-butyl-5-phenyl-3,4-dihydro-2H-pyrrole-2-carboxylate in the presence of chiral quaternary ammonium catalysts gave the corresponding alkylated products (up to 97% ee). The following diastereoselective reductions afforded chiral 5-phenyl-2-alkylprolines which can be applied to asymmetric synthesis as organocatalysts or synthesis of biologically active proline based compounds, such as chiral α-alkylated analogues of (+)-RP66803, as potential CCK antagonists.

Involvement of E2F1 transcriptional activity in cadmium‐induced cell‐cycle arrest at G1 in human lung fibroblasts

Human cadmium (Cd) exposure is associated with cancers of the lung and kidney. Using cDNA microarray analysis, we have recently reported that the expression of E2F1 is reduced by Cd in human lung fibroblasts, indicating the possibility of G1‐phase arrest. To test this hypothesis, we investigated the effects of Cd on the cyclin‐dependent kinase (CDK2) and retinoblastoma protein (Rb) regulatory pathways in WI38 human lung fibroblasts. We demonstrate here that G1‐phase accumulation was induced by Cd in WI38 (wild‐type for p53 and Rb), but not in the SV40 large T antigen‐transformed variant WI38‐VA13 (p53‐ and Rb‐defective). Cd‐induced cell‐cycle arrest was associated with a decrease in CDK2 protein and with increase in p21 expression and p53 phosphorylation. Cd treatment caused a distinct increase in the formation of p21‐cyclin E‐CDK2 complex, as revealed by immunoprecipitation. The level of Rb‐E2F1 complexes was increased, and the translocation of E2F1 to the nucleus was decreased by Cd treatment. Consequently, the transcriptional activity of E2F1 and the expression of the E2F1 target genes were also decreased by Cd. These results clearly demonstrate that Cd‐mediated G1 arrest in WI38 cells is associated with the suppression of Rb phosphorylation and with the inhibition of E2F1 transcriptional activity. Environ. Mol. Mutagen. 52:145–152, 2011.