EN
Matrix metalloproteinases (MMPs) form an enzyme family which, by mainstream research, is implicated in extracellular matrix processing in physiological and pathophysiological conditions. Some of these proteins termed gelatinases, in particular MMP-2 and MMP-9, cleave gelatin as an artifi cial substrate. Surprisingly, a number of studies have revealed the presence of gelatinolytic activity in the cell nucleus. Although the phenomenon appears not to be artifactual, neither the identity nor the role of nuclear gelatinases has been established unequivocally. In the nervous system, nuclear gelatinolysis is detectable in normal conditions, yet it is induced by seizures, and stroke. We studied nuclear gelatinolytic activity by high resolution in situ zymography (ISZ) in sections of alcohol-fi xed, polyester wax-embedded normal rat brain. Ubiquitously distributed among the major brain areas the ISZ signal was present mainly in neurons. At high magnifi cation, our study revealed previously unrecognized mesh-like pattern of nuclear gelatinolytic which, by counterstaing with fl uorescent DNA-binding dye, represents an interchromatin space. The ISZ signal colocalized with the ribonucleoprotein compartment enriched in splicing components, identifi ed using an immunoreactivity of spliceosome assembly factor SC-35. This suggesting a function for MMPs in processes of gene-expression and/or RNA-processing and hypothetically involvement in remodeling of chromosome territories.