Nuclear localization of BCR and cortactin indicates their potential role in regulation of actin branching in nucleus.

AIM: To study cellular localization of full-length breakpoint cluster region (BCR), Pleckstrin homology domain of BCR and cortactin and determine whether they can coexist in cell nucleus. MATERIALS AND METHODS: HEK293T cell line was transfected with pECFP-BCR, pEGFP-PH and pmTagRFP-N1-CTTN using polyethyleneimine. Live cells were imaged in cell culture dishes with glass coverslip attached to the bottom with Leica SP8 STED 3D confocal microscope in the environmental chamber. Obtained images were processed and analyzed with Fiji software. RESULTS: We identified colocalization of full-length BCR and cortactin in nucleus of cell undergoing terminal phase of cell division. We did not observe nuclear localization of cortactin in non-dividing cell. Both Pleckstrin homology domain and full-length BCR exhibited cytoplasmic as well as nuclear localization. CONCLUSIONS: Colocalization of BCR with cortactin in cell nucleus indicates their potential role in regulation of actin network allowing for the maintenance of nuclear architecture and DNA integrity.

Colocalization of USP1 and РН domain of Bcr­Abl oncoprotein in terms of cronic myeloid leukemia cell rearrangements.

The development of chronic myeloid leukemia (CML) is the result of a reciprocal translocation between chromosomes 9 and 22 due to the emergence of Philadelphia chromosome. The product of this mutation is a hybrid oncoprotein Bcr-Abl. According to the results of mass spectrometric analysis, USP1 protein was identified as a potential candidate for interaction with the PH domain Bcr-Abl oncoprotein. Due to the deubiquitination properties, USP1 protein can prevent proteasomal degradation of Bcr-Abl oncoprotein in a cell and, consequently, contribute to its accumulation, and the progression of the disease. In this work, creating the genetic constructs, we detected the USP1 protein localization in the cell. Also, a nuclear colocalization of USP1 protein with PH domain of Bcr-Abl oncoprotein in HEK293T cells was shown. The results are important for understanding the implications of the Philadelphia chromosome emergence, and the development of new methods for CML treatment, since the recent techniques are not always effective due to the emergence of numerous mutations that cause drug resistance and relapse of the disease.