The most common translocation in human lymphoma, the t(14;18)(q32;q21), generates heterogeneous 4.2‐7.2 kb Bcl‐2‐immunoglobulin (Ig) chimeric mRNAs resulting from alternative Bcl‐2 5′ exons and varied Ig 3′ untranslated regions (UT). The normal human Bcl‐2 gene has a three exon structure with an untranslated first exon, a facultative 220 bp intron I, but an enormous 370 kb intron II. S1 protection and primer extension analysis defined initiation sites in exon II associated with classic promoter elements and a decanucleotide (ATG‐CAAAGCA) homologous with Ig variable region enhancers. Multiple initiation sites were also found in a GC‐rich region with Sp1 binding motifs in exon I. Most t(14;18) breakpoints cluster within the 3′ UT of Bcl‐2 implicating that event in gene deregulation. The Bcl‐2 gene introduced into the Ig constant (C gamma) locus of SU‐DHL‐6 displayed somatic mutation. While Bcl‐2–Ig mRNAs demonstrated an unaltered 2.5 h half‐life, the Bcl‐2–Ig gene revealed an inappropriately high rate of transcription for a mature B‐cell. This indicates the translocated Bcl‐2 allele has escaped normal control mechanisms.

The acetyl-transferase Tip60 might influence tumorigenesis in multiple ways. First, Tip60 is a co-regulator of transcription factors that either promote or suppress tumorigenesis, such as Myc and p53. Second, Tip60 modulates DNA-damage response (DDR) signalling, and a DDR triggered by oncogenes can counteract tumour progression. Using E(mu)-myc transgenic mice that are heterozygous for a Tip60 gene (Htatip) knockout allele (hereafter denoted as Tip60+/- mice), we show that Tip60 counteracts Myc-induced lymphomagenesis in a haplo-insufficient manner and in a time window that is restricted to a pre- or early-tumoral stage. Tip60 heterozygosity severely impaired the Myc-induced DDR but caused no general DDR defect in B cells. Myc- and p53-dependent transcription were not affected, and neither were Myc-induced proliferation, activation of the ARF-p53 tumour suppressor pathway or the resulting apoptotic response. We found that the human TIP60 gene (HTATIP) is a frequent target for mono-allelic loss in human lymphomas and head-and-neck and mammary carcinomas, with concomitant reduction in mRNA levels. Immunohistochemical analysis also demonstrated loss of nuclear TIP60 staining in mammary carcinomas. These events correlated with disease grade and frequently concurred with mutation of p53. Thus, in both mouse and human, Tip60 has a haplo-insufficient tumour suppressor activity that is independent from-but not contradictory with-its role within the ARF-p53 pathway. We suggest that this is because critical levels of Tip60 are required for mounting an oncogene-induced DDR in incipient tumour cells, the failure of which might synergize with p53 mutation towards tumour progression.

In a survey of 640 human subjects, a subgroup of 356 persons without recent exposure to antibiotics demonstrated that those with a high prevalence of Hg resistance in their intestinal floras were significantly more likely to also have resistance to two or more antibiotics. This observation led us to consider the possibility that mercury released from amalgam ("silver") dental restorations might be a selective agent for both mercuryand antibiotic-resistant bacteria in the oral and intestinal floras of primates. Resistances to mercury and to several antibiotics were examined in the oral and intestinal floras of six adult monkeys prior to the installation of amalgam fillings, during the time they were in place, and after replacement of the amalgam fillings with glass ionomer fillings (in four of the monkeys). The monkeys were fed an antibiotic-free diet, and fecal mercury concentrations were monitored. There was a statistically significant increase in the incidence of mercuryresistant bacteria during the 5 weeks following installation of the amalgam fillings and during the 5 weeks immediately following their replacement with glass ionomer fillings. These peaks in incidence of mercuryresistant bacteria correlated with peaks of Hg elimination (as high as 1 mM in the feces) immediately following amalgam placement and immediately after replacement of the amalgam fillings. Representative mercuryresistant isolates of three selected bacterial families (oral streptococci, members of the family Enterobacteriaceae, and enterococci) were also resistant to one or more antibiotics, including ampicillin, tetracycline, streptomycin, kanamycin, and chloramphenicol. While such mercury-and antibiotic-resistant isolates among the staphylococci, the enterococci, and members of the family Enterobacteriaceae have been described, this is the first report of mercury resistance in the oral streptococci. Many of the enterobacterial strains were able to transfer mercury and antibiotic resistances together to laboratory bacterial recipients, suggesting that the loci for these resistances are genetically linked. Our findings indicate that mercury released from amalgam fillings can cause an enrichment of mercury resistance plasmids in the normal bacterial floras of primates. Many of these plasmids also carry antibiotic resistance, implicating the exposure to mercury from dental amalgams in an increased incidence of multiple antibiotic resistance plasmids in the normal floras of nonmedicated subjects.

Neutral Re(V) and Tc(V) oxo complexes of the peptide dimethylglycyl-L-seryl-L-cysteinylglycinamide (RP294) were prepared and characterized by HPLC, spectroscopic techniques, and X-ray crystallographic analysis. The peptide was prepared as a single peptide chain using solid phase methods and characterized by HPLC and various spectroscopic techniques. The water-soluble Re(V) oxo complex of dimethylglycyl-L-seryl-L-cysteinylglycinamide [ReO(RP294)] was prepared from the reaction of the peptide with either [ReO(2)(en)(2)]Cl or ReOCl(3)(PPh(3))(2) in the presence of base. The complex exists as two isomers, the serine CH(2)OH group being in the syn oranti conformation with respect to the Re-oxo bond. The ratio of the isomers at room temperature is 1:1.1. The isomers were separated by reverse-phase HPLC, but the isolation of each isomer was complicated by their rapid interconversion in aqueous solution at room temperature. The molecular structure of the syn isomer of the Re complex was determined by X-ray crystallography. Crystals of syn-[ReO(RP294)] (C(12)H(20)N(6)O(5)ReS) are orthorhombic, of space group P2(1)2(1)2(1), with a = 6.954(1) Å, b = 8.0472(1) Å, c = 32.9183(4) Å, and Z = 4. The structure was solved by direct methods and was refined by full-matrix least-squares procedures to R = 0.0327 (R(w) = 0.0838) for 10 447 reflections with I > 2sigma(I). The Re metal was coordinated in a distorted square pyramidal geometry with the oxo moiety in the apical position. The peptide coordinated to ReO(3+) via the N(amine) atom of dimethylglycine, the S(thiolate) atom of cysteine, and the two N(amide) atoms of serine and cysteine (an N(2)N'S donor atom set). The Re atom lies approximately 0.74 Å above the distorted plane formed by the N(2)N'S donor atom set. Variable-pH (1)H NMR spectral data showed the Re complex was stable from pH 5 to 8.5. The reaction of (99)TcO(4)(-) with SnCl(2), sodium gluconate, and RP294 produced the (99)Tc(V) oxo RP294 complex, [(99)TcO(RP294)]. Like the [ReO(RP294)] complex, [(99)TcO(RP294)] also exists in the syn and anti conformations in a ratio of approximately 1:1. The (99m)Tc complex of RP294 was prepared at the tracer level from the reaction of Na[(99m)TcO(4)] with excess SnCl(2), sodium gluconate, and RP294. The (99m)Tc and Re RP294 complexes behaved similarly under identical HPLC conditions.

SpyTag is a peptide which spontaneously forms an amide bond to its protein partner SpyCatcher. Here we fused SpyTag at the N-terminus of β-lactamase and SpyCatcher at the C-terminus, so the partners could cyclize to lock together the termini of the enzyme. Wild-type enzyme aggregates above 37 °C, with irreversible loss of activity. Cyclized β-lactamase was soluble even after heating at 100 °C; after cooling, the catalytic activity was restored. SpyTag/SpyCatcher-cyclization achieved > 60 °C increase in stability, much larger than from point mutation or alternative approaches to cyclization. Cyclized dihydrofolate reductase was similarly resilient. Analyzing unfolding calorimetrically and via mutants, cyclization did not increase the unfolding temperature of β-lactamase, but facilitated refolding after thermal stress. SpyTag and SpyCatcher sandwiching represents a simple and efficient route for enzyme cyclization, with potential to greatly enhance the robustness of biocatalysts.