mAP kinases (MAPKs) are signal transduction intermediates for endogenous and environmental stimuli in diverse systems, ncluding growth regulation, carcinogenesis, and development. Activator protein-1 (AP-1) transcription factors regulate expression of genes in response to endogenous and extracellular stimuli, including hormones, growth factors, phorbol ester tumor promoters, and other carcinogenic agents. MAPKs are upstream regulators of AP-1. The mechanisms of AP-1 regulation by MAPKs in vivo are thought to involve direct MAPK phosphorylation of AP-1 components or to be indirect via signalling intermediates between MAPK and AP-1. We have identified a family of seven MAPK related proteins (MAPKRPs), including ERK-2, which forms stable complexes in vivo with (AP-1 transcription factors. While AP-1 proteins may be MPKRP substrates, the stability of complexes is an important clue that protein-protein interactions between MAPKRPs and AP-1 may have novel regulatory significance.
The aim of this program is to investigate the regulatory significance.
The aim of this program is to investigate the identities and funcitons of these numerous stable mAPK-AP-1 complexes. The genes encoding several MAPKRPs will be cloned by screening a Lambda ZAP Express cDNA library. Protein kinase activity of MAPKRPs and mAPK-AP-1 complexes will be measured by in vitro kinase assays. The hypothesis that MAPKRP-AP-1 complexes bind to AP-1 DNA will be tested by electrophoretic mobility shift and AP-1 DNA affinity chromatography assays. This program is significant because it is likely to lead to cloning of novel MAPKRP genes encoding MAPKRPs that bind AP-1 in vivo and shed light on mechanisms of MAPK and AP-1 signal transduction. If mAPKRP-AP-1-DNA complexes are discovered, it may provide a new paradigm for signal transduction complexes at the site of DNA. Since MAPKs and AP-1 mediate responses to many carcinogenic effectors, this work has potential significance for elucidating mechanisms of neoplastic transformation.
