Mechanism of interferon action: identification of a RNA binding domain within the N-terminal region of the human RNA-dependent P1/eIF-2 alpha protein kinase.

A molecular cDNA clone of the human RNA-dependent P1/eIF-2 alpha protein kinase was expressed in Escherichia coli. Mutant P1 proteins were examined for RNA binding activity by Northwestern blot analysis using the reovirus s1 mRNA, an activator of the kinase; the adenovirus VAI RNA, an inhibitor of kinase activation; or human immunodeficiency virus (HIV) TAR RNA as probe. Analysis of TrpE-P1 deletion mutant fusion proteins revealed that the 11-kDa N-terminal region of the P1 protein bound reovirus s1 mRNA, adenovirus VAI RNA, and HIV TAR RNA. Neither s1 RNA, VAI RNA, nor TAR RNA was bound by truncated P1 proteins which lacked the N-terminal 98 amino acids. Computer analysis revealed that the human protein P1 sequence corresponding to amino acid residues within the N-terminal RNA binding domain displays high homology (greater than 54% identity; 61 to 94% similarity) with two animal virus proteins which possess RNA binding activity (vaccinia virus E3L; rotavirus VP2) and two proteins of unknown function (murine TIK; rotavirus NS34), but which are likely RNA binding proteins.     

Cytokeratin 7/20 and MUC1, 2, 5AC, and 6 expression patterns in Barrett's esophagus and intestinal metaplasia of the stomach: intestinal metaplasia of the cardia is related to Barrett's esophagus.

Intestinal metaplasia (IM) in endoscopic biopsies obtained from close to the gastroesophageal junction may represent IM of the cardia (CIM) or Barrett's esophagus (BE), which have different malignant potentials despite similar morphology. This study compared cytokeratin (CK) 7/20 and mucin (MUC1, 2, 5AC, and 6) immunopatterns in biopsies from BE (n = 41), CIM (n = 35), and antral gastric IM (AIM, n = 37) to evaluate their roles as diagnostic aids. CK7 and CK20 expression was described as absent, patchy (superficial and deep), continuous superficial only, continuous deep only, and diffuse. Eleven different combinations of CK7/20 expression were seen. Since CK20 staining was positive in all cases, four main patterns were defined on the basis of the observed CK7 staining as 1, absent; 2, patchy (superficial and/or deep); 3, diffuse; and 4, continuous superficial only. Overall CK7 positivity (regardless of pattern) was higher in BE and CIM than in AIM. CK patterns 3 and 4 were also higher in BE and CIM than in AIM. For either pattern 3 or 4, the positive and negative predictive values for BE versus AIM were 95% and 67%, respectively. MUC1 was rarely expressed in BE and CIM compared with AIM, whereas the opposite was noted for MUC5AC expression. MUC2 and MUC6 expression was similar in all locations. In conclusion, diffuse or continuous superficial CK7 staining is highly characteristic of BE and CIM and contrasts with AIM. It is, however, not very sensitive. CK20 profiles have no added value. Mucin expression also differs between BE and CIM versus AIM, but the specificity of any pattern is insufficient for distinction in individual cases. Importantly, CK and MUC expression patterns in BE and CIM are virtually indistinguishable, limiting their use in this differential and raising the question of whether they are biologically related.