We have examined by fine mapping the S1 nuclease-hypersensitivity of the 5' flanking regions of the human beta-globin and rat preproinsulin II genes and of the SV40 origin/enhancer region. In all cases S1-hypersensitive sites are located in known or presumed promoter/regulatory regions. Though a consensus DNA sequence is not evident, all of these sites reside in predominantly homopurine-homopyrimidine stretches. The alternate (non-B) DNA structure which is revealed by the enzymatic probe is a sequence-dependent feature of a short stretch of DNA, which is retained upon transplantation into a foreign environment. The alternate structure exhibits S1-nicking patterns uniquely different from those associated with the presence of Z-DNA.

Hfq and other Sm proteins are central in RNA metabolism, forming an evolutionarily conserved family that plays key roles in RNA processing in organisms ranging from archaea to bacteria to human. Sm-based cellular pathways vary in scope from eukaryotic mRNA splicing to bacterial quorum sensing, with at least one step in each of these pathways being mediated by an RNA-associated molecular assembly built upon Sm proteins. Though the first structures of Sm assemblies were from archaeal systems, the functions of Sm-like archaeal proteins (SmAPs) remain murky. Our ignorance about SmAP biology, particularly vis-à-vis the eukaryotic and bacterial Sm homologs, can be partly reduced by leveraging the homology between these lineages to make phylogenetic inferences about Sm functions in archaea. Nevertheless, whether SmAPs are more eukaryotic (RNP scaffold) or bacterial (RNA chaperone) in character remains unclear. Thus, the archaeal domain of life is a missing link, and an opportunity, in Sm-based RNA biology.

To establish a method for separating different keratinocyte subpopulations in the epidermis, we studied the specificity of monoclonal antibody 4F2 for keratinocytes. Preliminary screening experiments had previously demonstrated 4F2 reactivity with the epidermis. 4F2 reacted with a subpopulation (19.29 +/- 5.23%) of human epidermal cells in suspension. The membrane antigen identified by 4F2 continues to be expressed by cultured keratinocytes. In frozen tissue section using an indirect immunofluorescence technique, the 4F2-positive cells in the basal layer are sharply demarcated from the negative suprabasilar layers. Even in the hyperproliferative state of psoriasis, the 4F2 reactivity is confined to the basal layer. Cell suspensions of psoriatic epidermis demonstrated a greater percentage of reactivity with 4F2 (49.51% +/- 6.50%), probably reflecting the expanded population of basal layer cells. Monoclonal 4F2, therefore, reacts with a membrane antigen present on basal keratinocytes, and provides a probe for use in the isolation of the basal keratinocyte subpopulation. Thus, this antibody should be useful in studies of normal and aberrant differentiation of the epidermis.

A series of monoclonal antibodies directed against T cell differentiation antigens was used to identify circulating T cells in normal human neonates. Twenty-five cord blood samples, taken after cesarean or vaginal delivery, and 16 venous blood samples from normal adult controls were examined using monoclonal antibodies in an indirect immunofluorescence technique. The percentage of circulating OKT3 positive (pan-T cell) cells was significantly lower in the neonatal blood (52.8%) compared with the adult controls (74.9%) (P less than .001). Of the cord mononuclear cells, 58% showed reactivity with OKT10 (common thymocyte antigen) compared with only 7% in adult controls (P less than .001). The helper:suppressor T cell ratio was lower in cord blood (1:2) as compared with 1:3 for adult blood (P less than .005) as observed in these studies. These figures reflect the presence of a significant population (25%) of immature T cells in cord blood that expresses simultaneously both helper (OKT4) and suppressor (OKT8) phenotypes. Twenty-four percent of the T cells in cord blood also expressed OKT6 antigen (cortical thymocyte), a feature not found in adult blood. Double-labeling studies characterized a previously undescribed blood T cell phenotype, which was simultaneously OKT6 and OKT3 (pan-T cell) positive; of the cells reactive with OKT3, 43% also were positive with OKT6. This study reveals the presence of immature populations of T cells in normal human neonatal blood exhibiting phenotypes characteristic of normal developing thymocytes and a previously undescribed cell phenotype.