Luman is a human basic leucine zipper transcription factor that, like the herpes simplex virus transcription factor VP16, requires the host cell factor, HCF, for activity. Although both HCF and Luman have been implicated in cell growth, their biological roles have not been clearly defined. Luman conforms to a type II membrane-associated glycoprotein with its carboxyl terminus embedded in cellular membranes and its amino terminus, which contains all its identified functional domains, in the cytoplasm. Here we show that Luman is processed by regulated intramembrane proteolysis (RIP). The site 1 protease (S1P), a Golgi apparatusresident enzyme responsible for catalyzing the first step in the RIP pathway of the sterol regulatory element binding proteins (SREBPs) and ATF6, may also be involved in the processing of Luman. Thus, processing of Luman was highly stimulated by brefeldin A, a compound that causes the reflux of Golgi apparatus enzymes to the endoplasmic reticulum (ER). In addition, coexpression of Luman with S1P containing a KDEL ER retrieval signal resulted in virtually quantitative cleavage of Luman in the absence of any treatment. Finally, Luman contains a sequence, RQLR, immediately downstream from the transmembrane domain which bears similarity to the consensus S1P cleavage site identified by others. Substitution of arginine residues within this motif abolished S1P cleavage, providing robust evidence that S1P is involved in Luman processing. We observed that following S1P cleavage, the majority of the cleaved Luman was retained in cytoplasmic membranes, indicating that an additional step or enzymes yet to be identified are involved in complete cleavage and release to yield the product which ultimately enters the nuclei of cells.Luman (also known as LZIP and CREB3) is a basic leucine zipper transcription factor of the CREB/ATF gene family. It possesses a potent N-terminal acidic activation domain and a basic-leucine zipper motif (bZIP) (15,(23)(24)(25)(26). The primary structure of Luman appears to be strongly conserved, and Luman homologues in mice (LZIP [8]), cattle (our unpublished results), and fruit flies (dCREB-A/BBF-2 [1, 37]) have been identified. We and others (15, 24) originally identified Luman when screening for cellular ligands of the human host cell factor (HCF, also known as C1 factor), a protein required by the herpes simplex virus (HSV) transactivator VP16. Luman interacts with HCF through the tetrapeptide DHTY (15,24,25), which is homologous to the EHAY HCF binding sequence of VP16. This motif, as (D/E)HXY, is conserved in the VP16 homologues of other alphaherpesviruses as well as in the homologues of Luman in mice, cattle, and fruit flies. Luman can bind and activate genes containing cyclic AMP response elements (CREs), although its natural target has not been identified. Similarly, although Luman has been implicated in the regulation of cell growth (18), its biological role in this process has not been clearly defined. Luman mRNA is present in a wide range of adult and fetal tissues (...

A number of viral and eukaryotic proteins which undergo a lipophilic modification by the enzyme N-myristoyltransferase (NMT: NMT1 and NMT2) are required for signal transduction and regulatory functions. To investigate whether NMT2 contributes to the pathogenesis of colorectal carcinoma, we observed a higher expression of NMT2 in most of the cases of cancerous tissues compared to normal tissues (84.6% of cases; P < 0.05) by Western blot analysis. Furthermore, protein-protein interaction of NMTs revealed that m-calpain interacts with NMT1 while caspase-3 interacts with NMT2. Our findings provide the first evidence of higher expression of NMT2 in human colorectal adenocarcinomas and the interaction of both forms of NMT with various signaling molecules.

Histone deacetylase inhibitors (HDIs) induce cell cycle arrest, differentiation and/or apoptosis in numerous cancer cell types and have shown promise in clinical trials. These agents are particularly novel, given their ability to selectively influence gene expression. Previously, we demonstrated that the HDIs butyrate and trichostatin A (TSA) directly repress c-Src proto-oncogene expression in many cancer cell lines. Activation and/or overexpression of c-Src have been frequently observed in numerous malignancies, especially of the colon. Therefore, our observation was particularly interesting since butyrate is a naturally abundant component of the large intestine and has been suggested to be a cancer-preventive agent. However, c-Src is not the only Src family kinase (SFK) member to be implicated in the development of human cancers, including those of the colon. Therefore, the relative expression levels of known SFKs were examined in a panel of human colon cancer cell lines. We found a surprisingly diverse expression pattern but noted that most cell lines expressed relatively high levels of at least 2 SFKs. When the effects of butyrate and TSA were examined in representative cell lines, the expression of all SFKs was repressed in a dose-and time-dependent manner. Further, detailed examination of Lck, Yes and Lyn demonstrated that this repression had a direct effect on transcription and was independent of new protein synthesis. These results mirror our earlier data obtained with c-Src and suggest that SFKs are a major target of HDIs and likely account in part for the anticancer effects of these promising new drugs. ' 2005 Wiley-Liss, Inc.

Saskatchewan has relatively high rates of mortality and 30-day rebleeding among patients with NVUGIB compared with published rates. The improved outcomes observed in the RQHR, when compared with the SHR, may be related to the employ of a formal call-back endoscopy team for the treatment of NVUGIB.