The protein composition of the hepatocyte nuclear matrix is differentiation-stage specific

The protein composition of hepatocyte nuclear matrices was examined in rats from the 16th day of gestation to 75 days after birth (adult), An overall increase in size of the nuclear matrix was accompanied by quantitative and qualitative changes in its protein content. Quantitative changes of the maj or proteins of the peripheral lamina surrounding the isolated nuclear matri x were detected. By Western analysis we established that in pre- and postna tal nuclear matrices the relative concentrations of lamin C mere greater th an lamin A. After birth, the relative concentrations of both lamins progres sively increased, In the adult nuclear matrix, the concentration of lamin A was greater than lamin C, In contrast, the relative concentrations of lami n B remained unchanged throughout development and growth. The relative conc entrations of two nuclear matrix-associated regulatory proteins studied cha nged with development and growth: transcription factor C/EBP alpha isoforms , which were detected during the gestation period, increased notably after the first postnatal day, attaining a maximum at the adult stage; the high c oncentrations of the proliferating cell nuclear antigen (PCNA) perceptibly decreased after the 21st prenatal day. Changes in the composition of the nu clear matrix protein suggest that this structure coordinates nuclear functi oning during cell differentiation.