| DC-SIGN (DC-specific intercellular adhesion molecule-3-grabbing nomntegrin) is a surface protein on dendritic cells(DCs), and plays an pivotal role on HIV infection. The structure of DC-SIGN includes four parts, namely, endocellular domain, transmembrane region, neck region (also named repeat region) and carbohydrate recognition domain (CRD). An investigation to 150 Caucasian suggested DC-SIGN repeat region normally consisted of six to eight alleles, with 99.52% of the population having seven, which served as wild genotypes. Repeat alleles in neck region can stabilize the structure of DC-SIGN. Variations in neck repeat region will impact the stabilization of DC-SIGN, resulting potential functional impairments of DC-SIGN. A group of foreign colleagues found DC-SIGN with homozygous 7/7 repeats was dominant genotye in HIV infected individuals, whereas heterozygous repeats variations were not found in those individuals, suggesting people with Homozygous 7/7 repeats of DC-SIGN were at risk of HIV infection, while people with heterozygous repeat variations were not susceptible to HIV infection. For further elucidating relationship between variations of repeat region and HIV infection susceptibility, we designed specialized PCR primers for DC-SIGN repeat region, and investigated this region among HIV infected Chinese and Germans by PCR amplification. The agarose gel electrophoresis andsequencing analysis showed that there were 8/8R 8/7R 7/7R 7/6R 7/5R 6/6R genotypes in 120 healthy control and 8/8R 8/7R and 7/7 R variations in HIV infected 119 Chinese. In addition, 8/8R 8/7R 8/6 R 7/7R 7/6R 7/5R 6/6R. 6/5R. 5/5R genotype viariations were detectedin HIV infected 132 Germans. Date analysis indicated that there were no significant discrepancies of DC-SIGN genotypes between HIV-seropositive individuals and healthy control. Different from previous reports, our results showed that heterozygous genotypes could be found in HIV infected individuals. Whether or not the heterozygous genotypes of DC-SIGN reduce the susceptibilities to HIV infection should be reconsidered. At least, our date indicated that heterozygous DC-SIGN did not reduce the risk to HIV infection in Chinese populations.DC-SIGN gene promoter is great of importance to functions of DC-SIGN, associating with gene expression efficiency and level. DC-SIGN mainly presented on DCs in dermal and lymphatic tissues. Limited expressions of DC-SIGN in vivo on some cells and tissues were associated with DC-SIGN regulatory mechanisms. For better understanding of characters of DC-SIGN promoter, we isolated DC-SIGN gene promoter and cloned it into luciferase reporting vector pGL3-Basic and pGL3-Enhancer respectivly, then transfected it into adherent cell lines. DC-SIGN promoter activities were assayed by detection of luciferase activities. The results indicated DC-SIGN promoter were a weak promoter in vitro study, which could only induce a weak expression of DC-SIGN in vitro under the condition of Enhancer existence.DC-SIGN promter region is located within +251-+487 nucleotide at 5' flank of DC-SIGN, with 5 nuclear transcriptional binding protein site in this region including NF-κB binding site. For further research about the regulatory character of DC-SIGN promoter, we constructed a mutant of DC-SIGN promoter with NF-κB site deletion. We transfected this mutant and NF-κBp50 expression vector to THP-1 cells, respectively, to observe IL-4 and NF-κB effects on DC-SIGN expression. The results revealed the deletion of NF-κB site within promoter region reduced the activities ofDC-SIGN about 50%, at the same time, NF-κBp50 expression in THP-1 cells resulted to DC-SIGN expression. Those results suggested DC-SIGN expression were associated with NF-κBp50. IL-4 enhanced the activities of DC-SIGN promoter, and induced DC-SIGN expression, revealing IL-4 induction to DC-SIGN was related to DC-SIGN promter.
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