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The biochemical and biophysical properties of mucins are largely determined by extensive O-glycosylation of serine- and threonine-rich tandem repeat (TR) domains. In a number of human diseases aberrant O-glycosylation is associated with variations in the properties of the cell surface–associated and secreted mucins. To evaluate in vivo the O-glycosylation of mucin TR domains, we generated recombinant chimeric mucins with TR sequences from MUC2, MUC4, MUC5AC, or MUC5B, which were substituted for the native TRs of epitope-tagged MUC1 protein (MUC1F). These hybrid mucins were extensively O-glycosylated and showed the expected association with the cell surface and release into culture media. The presence of different TR domains within the chimeric mucins appears to have limited influence on their posttranslational processing. Alterations in glycosylation were detailed by fast atom bombardment mass spectrometry and reactivity with antibodies against particular blood-group and tumor-associated carbohydrate antigens. Future applications of these chimeras will include investigations of mucin posttranslational modification in the context of disease.

Defensins are antimicrobial peptides which play a key role in innate immunity. High levels of human beta defensin‐1 (hBD‐1) have previously been detected in the kidney and pancreas, but the cell‐specific location of hBD‐1 mRNA has not been determined. The expression of hBD‐1 mRNA has been examined in fetal and adult pancreas and kidney by mRNA in situhybridization. In fetal pancreas, hBD‐1 expression was detected in the developing acini and in adult pancreas in the acini, but not in the pancreatic ducts. In both fetal and adult kidney, hBD‐1 expression was detected in the collecting ducts and in the loops of Henle in adult kidney. Expression of hBD‐1 mRNA in the pancreas and kidney from early development and in the acini of the adult pancreas, rather than in the pancreatic ducts, may indicate that in these tissues, hBD‐1 fulfils physiological functions in addition to host defence. © 1998 John Wiley & Sons, Ltd.

Defensins are antimicrobial peptides which play a key role in innate immunity. High levels of human beta defensin-1 (hBD-1) have previously been detected in the kidney and pancreas, but the cell-specific location of hBD-1 mRNA has not been determined. The expression of hBD-1 mRNA has been examined in fetal and adult pancreas and kidney by mRNA in situ hybridization. In fetal pancreas, hBD-1 expression was detected in the developing acini and in adult pancreas in the acini, but not in the pancreatic ducts. In both fetal and adult kidney, hBD-1 expression was detected in the collecting ducts and in the loops of Henle in adult kidney. Expression of hBD-1 mRNA in the pancreas and kidney from early development and in the acini of the adult pancreas, rather than in the pancreatic ducts, may indicate that in these tissues, hBD-1 fulfils physiological functions in addition to host defence. © 1998 John Wiley & Sons, Ltd.

Cosmid‐borne and chromosomal lacZfusions to aapJ, aapQand aapMwere used to examine the nitrogen regulation of the general amino acid permease (Aap) of Rhizobium leguminosarumstrain 3841. Transcription of the first gene of the operon (aapJ), which encodes the periplasmic binding protein, was 2–4‐fold higher than aapQand aapM, which encode the integral membrane proteins, under various growth conditions. This may be due to the presence of a putative stem loop in the intergenic region between aapJand aapQ. All aapfusions were derepressed 3–5‐fold after growth on glutamate as a nitrogen source, which effectively causes nitrogen limitation. An ntrCmutant was derepressed for transcription of the aapoperon and had high rates of amino acid transport when grown on ammonia as the nitrogen source. Thus NtrC negatively regulates the aapoperon, contrary to its usual role in positive gene activation. These results confirm that the aapoperon is subject to complex regulation involving both transcriptional and post‐transcriptional factors.

MUC1 is expressed at the apical surface of ductal epithelia of tissues, including breast, pancreas, airway, and the gastrointestinal tract, where its functions include lubrication and protection of the epithelia. In addition, roles for MUC1 have been suggested in both adhesive and antiadhesive properties of tumor cells, and extensive O-glycosylation of the MUC1 tandem repeat domain may contribute to these functions. Little information is available on the specific O-glycosylation of MUC1. One problem in identifying different MUC1 glycoforms has been that monoclonal antibodies raised against the MUC1 core protein recognize epitopes in the tandem repeat domain, which is often glycosylated to an extent that obscures these epitopes. We developed an epitope-tagged form of MUC1 that allowed the detection of multiple MUC1 glycoforms and established the presence of a number of important blood group and tumor-associated carbohydrate antigens on MUC1 expressed by two pancreatic tumor cell lines (Panc-1 and S2-013) and two colon tumor cell lines (Caco-2 and HT-29). Antigens detected include sialyl-Lewisa, sialyl-Lewisc, sialyl-Lewisx, and sialyl-Tn.

Cosmid-borne and chromosomal lacZ fusions to aapJ, aapQ and aapM were used to examine the nitrogen regulation of the general amino acid permease (Aap) of Rhizobium leguminosarum strain 3841. Transcription of the first gene of the operon (aapJ), which encodes the periplasmic binding protein, was 2–4-fold higher than aapQ and aapM, which encode the integral membrane proteins, under various growth conditions. This may be due to the presence of a putative stem loop in the intergenic region between aapJ and aapQ. All aap fusions were derepressed 3–5-fold after growth on glutamate as a nitrogen source, which effectively causes nitrogen limitation. An ntrC mutant was derepressed for transcription of the aap operon and had high rates of amino acid transport when grown on ammonia as the nitrogen source. Thus NtrC negatively regulates the aap operon, contrary to its usual role in positive gene activation. These results confirm that the aap operon is subject to complex regulation involving both transcriptional and post-transcriptional factors.