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We have identified and analyzed a 27-nucleotide sequence (U5 repressive element, designated as USRE) at the U5 region of the human T-cell leukemia virus type I (HTLV-I) long terminal repeat (LTR) which is required for HTLV-I basal transcriptional repression. The basal promoter strength of constructs that contained deletions in the U5 region of the LTR was analyzed by chloramphenicol acetyltransferase (CAT) assays following transfection of HeLa cells or Jurkat T-cells in the presence or absence of viral transactivator tax protein. We consistently observed a 2-to 5-fold increase in basal promoter activity when sequences between +277 to +306 were deleted. In vivo competition experiments suggested that the U5 DNA fragment from +269 to +295 contains a functional repressive element (USRE). Using gel mobility shift assays, we have purifled a highly enriched fraction that could specifically bind USRE. This DNA afbnity column fraction contained three major detectable proteins on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with silver staining: llO-, 80-and 'IO-kDa proteins. The llO-kDa protein appeared to be a novel DNA-binding protein whose characteristics are still obscure, while the 70-and IO-kDa proteins were shown to be related to the human autoantigen Ku, the Ku (p701p80) complex, as demonstrated by amino acid sequencing and immunological analyses. As Ku is known to be involved in transcriptional regulation, the specific interaction of Ku with USRE raises intriguing possibilities for its function in Hl?_V-I basal transcriptional repression.Key words: Human T-cell leukemia virus type I (HTLV-I); DNA binding protein; Ku protein; Transcriptional repression IutroductionHuman T cell leukemia virus type I (HTLV-I) is an exogenous human retrovirus that has been shown to be the etiologic agent of a type of acute T-cell leukemia, known as adult T-cell leukemia (ATL), as well as a neurological disorder, known as HTLV-I-associated myelopathy or tropical spastic paraparesis (HAMfTSP) [l-6], and an eye disease, HTLV-I uveitis [7]. The latter two diseases are considered to be outcomes of immune disorders caused by HTLV-I infection. After infection into humans, the virus requires a long latent period until the onset of such diseases [8]. The full mechanism of the viral latency has not been uncovered yet. Analysis of HTLV-I gene expression in vitro, however, provides some important information on the mechanisms of the viral latent infection and activation from the latent state.After integrating into host chromosomal DNA, the expression of the viral genes is known to be regulated by various viral and host nuclear factors through the viral 5' long terminal repeat (LTR). The 21-bp repeat elements, TRE-1 (HTLV-I-tax protein responsive element l), are required for the transactivation of the HTLV-I tax protein that is reported to bind indirectly to the enhancer elements through host cell nuclear factors [9-l 11. The cellular nuclear factors such as SPl, TIF-1, Ets and Myb interact with the LTR at the region located...

In our previous study, the MDR1/Pglycoprotein-overexpressing multidrug resistant subline, Hvr100-6, was established from the human cervical carcinoma cell line HeLa-Ohio (HeLa) by stepwise exposure to an anti-microtubule agent, vinblastine sulfate, a typical substrate of MDR1. Their gene and protein expression profiles were analyzed herein, and 148 genes were identified to be differentially expressed by cDNA microarray analysis. The up-regulation of sorcin, a soluble resistance-related calcium-binding protein of 22 kDa, was confirmed in Hvr100-6 cells by the proteome analysis. To clarify the relationship between MDR1 and sorcin, HeLa cells were treated with small interfering RNAs (siRNAs) targeted for theirs mRNAs. The siRNA for MDR1 mRNA resulted in its decrease by 86% and 61% on the days 1 and 2 after the treatment, whereas the expression level of sorcin mRNA was not changed. On the other hand, the siRNA for sorcin mRNA suppressed its expression by 80-90% on days 1-3 after the treatment. Interestingly; suppression of sorcin induced a more than 3-fold increase in the expression level for MDR1 mRNA. An efflux function of MDR1 evaluated with using rhodamine 123 as a probe showed a tendency to be increased in HeLa cells treated with siRNA for sorcin, compared with that in the cells treated with scramble siRNA. The activity and the expression of caspase-3 in the sorcin knock-down HeLa cells were relatively higher than those in the cells treated with scramble siRNA. Thus, we demonstrated that sorcin might be a partial suppressor of MDR1 expression. Furthermore, the present study suggested that sorcin repressed apoptosis via dysfunction of caspase-3.

ultidrug resistance (MDR) is one of the most serious problems responsible for the failure of chemotherapy, and cellular factors associated with MDR include: 1) down-regulation of uptake or induction of the efflux system (e.g. MDR1 (P-glycoprotein)); 2) induction of inactivation enzymes including GSH-S-tranferase; 3) alteration of targeted enzymes including topoisomerase; 4) changes in DNA repair processes; and 5) alteration of apoptotic mechanisms.

In order to provide a device releasing drugs in a controlled manner and having targetability to specific organs or cells, chitosan-gel microspheres, CMS, crosslinked with glutaraldehyde, immobilizing 1-[N-(5-aminopentyl) carbamoyl]-5-fluorouracil, 1, coated with anionic polysaccharides, such as 6-O-carboxymethyl-N-acetyl-alpha-1,4-polygalactosamine (CM-NAPGA), 6-O-carboxymethyl-chitin, alginic acid and heparin, by polyelectrolyte complex membrane formation were prepared. When chitosan was crosslinked with glutaraldehyde, 1 was simultaneously immobilized into CMS by Schiff's base formation. Average diameter of CMS obtained was estimated to be about 0.5-1.0 micron by SEM observation. In physiological saline media, only free 5-FU was released from the CMS but 1 and any 5-FU derivative was not. Release rate of 5-FU from the CMS was reduced by coating with polyelectrolyte complex membrane of cationic chitosan and anionic polysaccharides. CMS coated with CM-NAPGA showed a lectin-mediated specific aggregation phenomenon by addition of Abrus precatorius agglutinin. Moreover, the CMS immobilizing 1 coated with CM-NAPGA showed higher growth-inhibitory effect against SK-Hep-1 (human hepatoma) cells in vitro than the CMS coated with other polysaccharides.