Brian K. Martin

Induction of MHC Class I Expression by the MHC Class II Transactivator CIITA

Major histocompatibility complex (MHC) class I-deficient cell lines were used to demonstrate that the MHC class II transactivator (CIITA) can induce surface expression of MHC class I molecules. CIITA induces the promoter of MHC class I heavy chain genes. The site alpha DNA element is the target for CIITA-induced transactivation of class I. In addition, interferon-gamma (IFNgamma)-induced MHC class I expression also requires an intact site alpha. The G3A cell line, which is defective in CIITA induction, does not induce MHC class I antigen and promoter in response to IFNgamma. Trans-dominant-negative forms of CIITA reduce class I MHC promoter function and surface antigen expression. Collectively, these data argue that CIITA has a role in class I MHC gene induction.

Two Distinct Domains within CIITA Mediate Self-Association: Involvement of the GTP-Binding and Leucine-Rich Repeat Domains

ABSTRACT CIITA is the master regulator of class II major histocompatibility complex gene expression. We present evidence that CIITA can self-associate via two domains: the C terminus (amino acids 700 to 1130) and the GTP-binding domain (amino acids 336 to 702). Heterotypic and homotypic interactions are observed between these two regions. Deletions within the GTP-binding domain that reduce GTP-binding and transactivation function also reduce self-association. In addition, two leucine residues in the C-terminal leucine-rich repeat region are critical for self-association as well as function. This study reveals for the first time a complex pattern of CIITA self-association. These interactions are discussed with regard to the apoptosis signaling proteins, Apaf-1 and Nod1, which share domain arrangements similar to those of CIITA.

Effects of paclitaxel on cytokine synthesis by unprimed human monocytes, T lymphocytes, and breast cancer cells

Abstract Paclitaxel or Taxol has attracted a great deal of attention in recent years because of its immense success as a chemotherapeutic agent for numerous types of cancer. It is known that paclitaxel stabilizes microtubules, and this characteristic is the presumed primary mechanism for its antitumor activity. Recently, however, paclitaxel’s ability to regulate gene expression, particularly in the murine system, has been reported by several groups. Here, we present research examining paclitaxel’s ability to alter expression of the interleukin-1β (IL-1β) and IL-8 cytokines in primary human monocytes, T lymphocytes, and four human breast cancer cell lines: MCF-7, ZR-75-1, MDA-MB-468, and MDA-MB-231. This report shows for the first time that treatment with 5–50 μM paclitaxel increases steady-state levels of IL-1β mRNA in unprimed human monocytes, MCF-7, and ZR-75-1 cells. Monocytes from eight donors in 16 experiments showed increased IL-1β secretion upon treatment; however, the increase in IL-1β production by monocytes was predicated on culturing in the absence of fetal bovine serum or in the presence of autologous human serum. In contrast to the IL-1β results, paclitaxel did not have significant effects on IL-8 expression by monocytes, T lymphocytes, or the breast cancer cells. These data show a specific effect of paclitaxel on cytokine synthesis by both immune cells and cancer cells.