2 NUCLEAR PROTEINS IN TRACHEAL EPITHELIAL-CELLS ARE RECOGNIZED BY ANTIBODIES SPECIFIC TO A SQUAMOUS DIFFERENTIATION MARKER, SPRI

In cell-free translations of RNA from primary cultures of pig trachea surface epithelial cells we observed that a mRNA encoding a 20 kDa pro line-rich protein (sPRP) was dramatically induced during culturing (Te sfaigzi et al., 1990, Biochem. Biophys. Res. Commun., 172:M1304-1309). This mRNA was not detected in tracheal tissue or in epithelial cells prior to culturing. Antisera were raised to synthetic peptide sequence s corresponding to 23 amino acids on the C-terminus (C23-antiserum) an d 29 amino acids on the N-terminus (N29 antiserum) of sPRP. On Western blot analysis, C23 antiserum reacted with a 20 kDa protein in cytosol ic extracts from pig tracheal cells maintained in culture for 4 days. The reaction with the 20 kDa protein was inhibited by adding C23 pepti de. Two nuclear proteins (66 and 70 kDa) obtained by micrococcal nucle ase treatment of tracheal cell nuclei were detected on Western blots w ith C23 antiserum. These proteins were present in cells both before an d after culturing. Sucrose gradient fractionation indicated that these nuclear proteins are associated with chromatin. Small amounts of the 66 and 70 kDa proteins were obtained from nuclear matrix fractions. Th ese nuclear proteins also reacted with N29 antiserum. Since these prot eins share similar epitopes with the N- and C-termini of sPRP, it is l ikely that the 20 kDa protein (sPRP) is part of these proteins. Howeve r, purification of the nuclear proteins followed by an amino acid sequ ence analysis is necessary to clarify whether sPRP is part of these pr oteins. (C) 1995 Wiley-Liss, Inc.