ХАВДАР ЭСИЙН ҮЙЛ АЖИЛЛАГААНД JSAP (JNK/STRESS-ACTIVATED PROTEIN KINASE-ASSOCIATED PROTEIN) УУРГИЙН ОРОЛЦОО

JSAP1 and JSAP2 are structurally close related family proteins and originally have been identified as scaffold proteins of the JNK and p38 MAPK modules. The specificity of MAPK cascades is regulated, at least in part, by scaffold proteins, such as JSAPs[1-7]. Some studies showed [7-12] that JSAPs function as adaptor proteins which link cargoes to kinesin-1, the cellular cargo transporter along with microtubules. Also JSAPs regulate certain crucial neuronal processes, particularly axon elongation, branching and neurite outgrowth[13-22]. Interestingly, in recent studies it was reported that an elevated expression of JSAP2 protein in various cancers, including breast, colorectal cancer and hepatocellular carcinoma, might be proposed as a biomarker for diagnosis of cancers at early stage[25-28]. However, roles of JSAP in cancer cells and their underling molecular mechanisms are not known well at present. Within our project which aims to clarify potential roles of JSAPs in cancers, in the present study an overexpression of JSAPs in HeLa cells using lentiviral vectors were performed and immunocytochemical analyses focused on centrosomes at mitotic stage of dividing cells were done. In results, in HeLa dividing cells, which overexpress the wild type of JSAPs or their substitution mutant forms a multiple centrosome at mitotic stage of cells were found. However, in case of overexpression of the deletion mutant JSAP proteins in cancer cells a multi-centrosome abnormality were not observed, as well as in control cells.

Conditional Transgenic System for Mouse Aurora A Kinase: Degradation by the Ubiquitin Proteasome Pathway Controls the Level of the Transgenic Protein

ABSTRACT Aurora A is a mitotic kinase that localizes to centrosomes. Expression of this protein is normally limited to the mitotic stage (G2-M) of the cell cycle, whereas human cancer cells frequently exhibit overexpression of Aurora A protein regardless of the cell cycle stage. In the present study, Aurora A transgenic mouse lines were generated with a new conditional expression system (cytomegalovirus immediate early enhancer-chicken beta-actin hybrid promoter-Z-enhanced green fluorescent protein) in order to analyze the function of this protein. Although transcripts for Aurora A were elevated in multiple organs of the transgenic mice, the corresponding protein was not detected in extracts analyzed by immunoblotting. The treatment of transgenic-derived embryonic fibroblasts (MEF) with proteasome inhibitors markedly increased the protein level of transgenic Aurora A, indicating that the transgenic Aurora A protein is readily degraded in normal mouse tissues. Under the exponential growth conditions of MEF cells, transgenic Aurora A was detected within the mitotic stage of the cell cycle and localized to centrosomes. In contrast, the marker of the transgenic promoter (enhanced green fluorescent protein) was continuously expressed throughout the cell cycle, indicating the constitutive transcription of transgenic mRNA. These results indicate that transgenic Aurora A is protected from degradation within G2-M but is immediately degraded after translation in the G1-S stage of the cell cycle. The findings obtained with this transgenic model and derived cells support that the transition from protection to degradation by the ubiquitin proteasome system at the end of mitosis is an important step in controlling the level of Aurora A protein during the cell cycle.