Genome-wide co-localization of active EGFR and downstream ERK pathway kinases mirrors mitogen-inducible RNA polymerase 2 genomic occupancy.

Genome-wide mechanisms that coordinate expression of subsets of functionally related genes are largely unknown. Recent studies show that receptor tyrosine kinases and components of signal transduction cascades including the extracellular signal-regulated protein kinase (ERK), once thought to act predominantly in the vicinity of plasma membrane and in the cytoplasm, can be recruited to chromatin encompassing transcribed genes. Genome-wide distribution of these transducers and their relationship to transcribing RNA polymerase II (Pol2) could provide new insights about co-regulation of functionally related gene subsets. Chromatin immunoprecipitations (ChIP) followed by deep sequencing, ChIP-Seq, revealed that genome-wide binding of epidermal growth factor receptor, EGFR and ERK pathway components at EGF-responsive genes was highly correlated with characteristic mitogen-induced Pol2-profile. Endosomes play a role in intracellular trafficking of proteins including their nuclear import. Immunofluorescence revealed that EGF-activated EGFR, MEK1/2 and ERK1/2 co-localize on endosomes. Perturbation of endosome internalization process, through the depletion of AP2M1 protein, resulted in decreased number of the EGFR containing endosomes and inhibition of Pol2, EGFR/ERK recruitment to EGR1 gene. Thus, mitogen-induced co-recruitment of EGFR/ERK components to subsets of genes, a kinase module possibly pre-assembled on endosome to synchronize their nuclear import, could coordinate genome-wide transcriptional events to ensure effective cell proliferation.

PR55α-containing protein phosphatase 2A complexes promote cancer cell migration and invasion through regulation of AP-1 transcriptional activity.

The proto-oncogene c-Jun is a component of activator protein-1 (AP-1) transcription factor complexes that regulates processes essential for embryonic development, tissue homeostasis and malignant transformation. Induction of gene expression by c-Jun involves stimulation of its transactivation ability and upregulation of DNA binding capacity. While it is well established that the former requires JNK-mediated phosphorylation of S63/S73, the mechanism(s) through which binding of c-Jun to its endogenous target genes is regulated remains poorly characterized. Here we show that interaction of c-Jun with chromatin is positively regulated by protein phosphatase 2A (PP2A) complexes targeted to c-Jun by the PR55α regulatory subunit. PR55α-PP2A specifically dephosphorylates T239 of c-Jun, promoting its binding to genes regulating tumour cell migration and invasion. PR55α-PP2A also enhanced transcription of these genes, without affecting phosphorylation of c-Jun on S63. These findings suggest a critical role for interplay between JNK and PP2A pathways determining the functional activity of c-Jun/AP-1 in tumour cells.

[Globoid cell leukodystrophy of adult. A first case in Poland]. / Leukodystrofia globoidalna doroslych. Pierwszy przypadek w Polsce.

Krabbe disease (globoid cell leukodystrophy) is a progressive, autosomal recessive disorder affecting peripheral and central nervous system. This disease is associated with mutation in GALC gene and its locus has been mapped to chromosome 14q31. GALC gene codes lysosomal hydrolytic enzyme: galactocerebroside ß-galactosidase (galactosylceramidase) which is crucial for degradation of galactolipids, mostly galactosylceramide and galactosylsphingosine (psychosine). The disease may be subdivided into four types: infantile form with onset within the first six months, child form presenting between 6 months and 3 years, juvenile form presenting between 3 and 10 years and the rarest adult form with onset after 10 years. The diagnosis of Krabbe disease is based on clinical findings and confirmed with galactocerebroside ß-galactosidase deficiency. We have found family with adult-onset disease. To our knowledge, this is the first observation of patient with adult form of Krabbe disease in Poland.