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Scaffold-associated regions (SARs) function at the level of modeling or shaping the chromatin of DNA into loop domains. We have mapped 36 SARs in the human type I interferon ( IFN ) gene complex on chromosome 9, band p21-22, to examine the overall structure of this gene complex. A total of 29 strong SARs and 7 weak SARs were mapped to the flanking regions of the different interferon genes. Twenty-two strong SARs mapped to the flanking regions of 13 interferon ( IFNA ) α genes; 2 strong SARs mapped to one interferon ω ( IFNW ) gene; 2 strong SARs mapped to one interferon α pseudogene ( IFNAP ); and 3 strong SARs mapped to two interferon ω pseudogenes ( IFNWP ). One weak SAR mapped to the flanking region of one IFNA gene, whereas 6 weak SARs flanked four IFN pseudogenes ( P11, P12 P20, P23 ). The IFN SAR structure was comparable between the BV173 leukemia cell line and the U373 glioma cell line. Analysis of two glioma deletion breakpoint junctions, where breaks occur within and outside the IFN gene cluster, revealed an association with SARs. IFN SARs showed evidence for cooperativity among the SARs, while DNA sequence analysis revealed a series of clustered A-tracts within strong SARs. These data suggest that the IFN genes may be organized into a series of small (2–10 kb) DNA loop domains, with each loop containing a coding region flanked by SARs. In our model, the SAR enrichment and the clustering of A-tracts observed at the SARs within the IFN gene complex represent a higher level of chromatin organization, which may predispose this region to breakage.

Tyrosine kinases are thought to play a major role in the control of cell growth and differentiation. Most of the work on the phosphorylated product was performed, however, on isolated proteins or cultured cell lines. To assess the overall involvement of tyrosine phosphorylation in vivo, a monoclonal antibody (MAb) against phosphotyrosine was applied to conventional histological sections of various tissues. With the immunoperoxidase staining method, two unique patterns of intracellular distribution of phosphotyrosine were identified among a large variety of normal tissues. (a) In many of the epithelia examined, a peripheral staining was observed, either at the apical aspect alone or at the entire contact region between neighboring cells. This pattern of staining seems to coincide with the distribution of a subset of cytoskeletal elements and requires pre-treatment with proteinase K. (b) In most steroidogenic tissues examined, vesicular cytoplasmic staining was evident, which seems to represent steroid-containing granules. In this case, proteolytic pretreatment is not essential and can be harmful. An extensive survey of human ovarian carcinoma biopsies failed to reveal any consistent staining pattern. These findings might indicate the involvement of tyrosine phosphorylation in basic cellular activities such as the assembly of the specialized cytoskeletal components.

The first step in splicing of pre-mRNA involves an intermediate lariat structure, in which a 2'5' phosphodiester bond between the 5' terminal guanosine residue of the intron and a specific adenosine residue near the 3' end of the intron is formed. A mammalian enzyme that generates 2'-5' phosphodiester bonds is (2'-5')oligoadenylate synthetase [(2'-5')OASE]. Although the expression of this enzyme is induced by interferon, low constitutive levels can be detected in untreated cells and tissues. The structural similarity between the lariat branch point and the 2'-5' phosphodiester bond generated by (2'-5')OASE prompted the experiments described here which suggest that this enzyme is involved in pre-mRNA splicing. (i) We show that a (2'-5')OASE activity is associated with 60S spliceosomes in an ATP- and RNA-dependent manner and that it can be indirectly immunoprecipitated by anti-Sm antibodies. (ii) Antibodies against (2'-5')OASE inhibit the lariat formation in the first step of splicing when added directly to a splicing reaction in vitro. (iii) HeLa cell nuclear extracts immunodepleted of (2'-5')OASE activity were also deficient in splicing activity.

Antibodies to a 56 kDa nuclear protein have been found in the sera of 85% of patients with myositis using an immunoblotting technique. This auto-antibody appears to be relatively disease-specific though more frequently detectable in both adult and childhood onset dermatomyositis. In adult patients with myositis the anti-56 kDa antibody level reflects disease activity. This antibody is thus much more frequently found than previously described disease-specific autoantibodies in patients with myositis such as the Jo-1 antibody, and may represent a useful diagnostic aid in patients with muscle weakness.