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Epidermal growth factor (EGF) and monoclonal antibody to cell surface EGF receptor bind to the same chromatin
E M Rakowicz-Szulczynska1, D Otwiaska, U Rodeck
1Wistar Institute of Anatomy and Biology, Philadelphia, Pennsylvania 19104.
Abstract:
Cellular uptake, nuclear translocation, and chromatin binding of epidermal growth factor (EGF) and monoclonal antibodies (MAbs) against the protein domain of the EGF surface receptor (MAb 425) and against the carbohydrate Y determinant on the EGF receptor (MAb Br 15-6A) were analyzed in cell lines that express surface EGF receptor. Both EGF and MAb 425 were translocated to the nucleus and bound in nondegraded form to the chromatin of all cells tested. MAb Br 15-6A was taken up only by SW 948 colorectal carcinoma cells which express EGF receptor whereas neither EGF nor MAb 425 was taken up by SW 707 colorectal carcinoma cells which do not express EGF receptor. MAb 425 immunoprecipitated a 230- to 250-kDa chromatin protein, which appears to be the EGF chromatin receptor. EGF was localized in a single EcoRI DNA fragment suggesting that the chromatin binding was highly specific. Binding of EGF to primarily DNase II-sensitive chromatin regions protected these regions from nuclease action. The role of growth factor binding to chromatin in neoplastic transformation is discussed.
Insights
Epidermal growth factor (EGF) and specific antibodies enter the nucleus and bind to chromatin. This binding, particularly of EGF, appears highly specific and may influence neoplastic transformation.
Area of Science:
- Cell Biology
- Molecular Biology
- Cancer Research
Background:
- The epidermal growth factor (EGF) receptor is crucial in cell signaling and implicated in cancer.
- Understanding the intracellular fate of EGF and its receptor interactions is vital for targeted therapies.
Purpose of the Study:
- To investigate the cellular uptake, nuclear translocation, and chromatin binding of EGF and specific monoclonal antibodies (MAbs) targeting the EGF receptor.
- To determine the specificity and nature of EGF-chromatin interactions.
Main Methods:
- Analysis of cellular uptake and nuclear translocation of EGF and MAbs in cell lines with varying EGF receptor expression.
- Chromatin binding assays and immunoprecipitation to identify interacting proteins and DNA fragments.
- Nuclease sensitivity assays to characterize chromatin regions involved in binding.
Main Results:
- Both EGF and MAb 425 translocated to the nucleus and bound to chromatin in all tested cells.
- MAb Br 15-6A uptake was restricted to cells expressing the EGF receptor.
- A 230- to 250-kDa chromatin protein was identified as the EGF chromatin receptor.
- EGF binding to chromatin was highly specific and protected DNase II-sensitive regions.
Conclusions:
- EGF and certain MAbs can access the cell nucleus and bind to chromatin.
- Specific interactions between EGF and chromatin components are demonstrated, suggesting a role in cellular processes.
- These findings provide insights into the nuclear functions of growth factors and their potential involvement in neoplastic transformation.