T-kininogen gene expression is induced during aging

Behavioral and molecular markers of death in Drosophila melanogaster

Fly movement was tracked through 3-dimensional (3D) space as the fly died, using either reflected visible light, reflected infrared (IR) light, or fly GFP fluorescence. Behaviors measured included centrophobism, negative geotaxis, velocity, and total activity. In addition, frequency of directional heading changes (FDHC) was calculated as a measure of erratic movement. Nine middle-aged flies were tracked as they died during normal aging, and fifteen young flies were tracked as they died from dehydration/starvation stress. Episodes of increased FDHC were observed 0-8 h prior to death for the majority of the flies. FDHC was also increased with age in flies with neuronal expression of a human Abeta42 protein fragment associated with Alzheimer's disease. Finally, green autofluorescence appeared in the eye and body immediately prior to and coincident with death, and fluorescence of GFP targeted to the retina increased immediately prior to and coincident with death. The results suggest the potential utility of FDHC, green autofluorescence, and retinal GFP as markers of neuronal malfunction and imminent death.

Proteomics Analysis to Identify and Characterize the Biomarkers and Physical Activities of Non-Frail and Frail Older Adults

Globally, the proportion of older adults is increasing. Older people face chronic conditions such as sarcopenia and functional decline, which are often associated with disability and frailty. Proteomics assay of potential serum biomarkers of frailty in older adults. Older adults were divided into non-frail and frail groups (n = 6 each; 3 males in each group) in accordance with the Chinese-Canadian Study of Health and Aging Clinical Frailty Scale. Adults were measured for grip power and the 6-min walk test for physical activity, and venous blood was sampled after adults fasted for 8 h. Ultra-high-performance liquid chromatography-tandem mass spectrometry was used for proteomics assay. The groups were compared for levels of biomarkers by t test and Pearson correlation analysis. Non-frail and frail subjects had mean age 77.5±0.4 and 77.7±1.6 years, mean height 160.5±1.3 and 156.6±2.9 cm and mean weight 62.5±1.2 and 62.8±2.9 kg, respectively. Physical activity level was lower for frail than non-frail subjects (grip power: 13.8±0.4 vs 26.1±1.2 kg; 6-min walk test: 215.2±17.2 vs 438.3±17.2 m). Among 226 proteins detected, for 31, serum levels were significantly higher for frail than non-frail subjects; serum levels of Ig kappa chain V-III region WOL, COX7A2, and albumin were lower. The serum levels of ANGT, KG and AT were 2.05-, 1.76- and 2.22-fold lower (all p < 0.05; Figure 1A, 2A and 3A) for non-frail than frail subjects and were highly correlated with grip power (Figure 1B, 2B and 3B). Our study found that ANGT, KG and AT levels are known to increase with aging, so degenerated vascular function might be associated with frailty. In total, 226 proteins were revealed proteomics assay; levels of angiotensinogen (ANGT), kininogen-1 (KG) and antithrombin III (AT) were higher in frail than non-frail subjects (11.26±2.21 vs 5.09±0.74; 18.42±1.36 vs 11.64±1.36; 22.23±1.64 vs 9.52±0.95, respectively, p < 0.05). These 3 factors were highly correlated with grip power (p < 0.05), with higher correlations between grip power and serum levels of ANGT (r = -0.89), KG (r = -0.90), and AT (r = -0.84). In conclusion, this is the first study to demonstrate a serum proteomic profile characteristic of frailty in older adults. Serum ANGT, KG and AT levels could be potential biomarkers for monitoring the development and progression of frailty in older adults.

Sex-specific alterations in chromatin conformation of the brain of aging mouse

Chromatin conformation has been analysed in the brain cortex of adult (24+/-2 weeks) and old (65+/-4 weeks) male and female mice. Nuclei purified from different groups of mice were digested with MNase and DNase I for varying time periods (0-90 min), and with endogenous endonucleases for 1 h. MNase and DNase I digestion kinetics showed that the percentage of acid solubility of chromatin was relatively lower in old than adult and in female than male. This was further supported by electrophoretic analysis of nuclease digested DNA fragments. When the nuclei were incubated with only Ca2+ or Mg2+, no endonuclease digestion was observed. However, under similar conditions, the liver DNA was cleaved substantially. When divalent cations were added together, they activated endogenous endonucleases and digested the brain chromatin. The activity of Ca2+/Mg2+-dependent endogenous endonucleases was higher in male than female. Thus the accessibility of chromatin to MNase, DNase I and endogenous endonucleases was higher in male than female, and MNase as well as DNase I were more active in adult than old. Such sex- and age-dependent conformation of chromatin may attribute to differential expression of genes in the mouse brain.

Effects of age on the posttranscriptional regulation of CCAAT/enhancer binding protein alpha and CCAAT/enhancer binding protein beta isoform synthesis in control and LPS-treated livers

The CCAAT/enhancer binding protein alpha (C/EBPalpha) and CCAAT/enhancer binding protein beta (C/EBPbeta) mRNAs are templates for the differential translation of several isoforms. Immunoblotting detects C/EBPalphas with molecular masses of 42, 38, 30, and 20 kDa and C/EBPbetas of 35, 20, and approximately 8.5 kDa. The DNA-binding activities and pool levels of p42(C/EBPalpha) and p30(C/EBPalpha) in control nuclear extracts decrease significantly whereas the binding activity and protein levels of the 20-kDa isoforms increase dramatically with LPS treatment. Our studies suggest that the LPS response involves alternative translational initiation at specific in-frame AUGs, producing specific C/EBPalpha and C/EBPbeta isoform patterns. We propose that alternative translational initiation occurs by a leaky ribosomal scanning mechanism. We find that nuclear extracts from normal aged mouse livers have decreased p42(C/EBPalpha) levels and binding activity, whereas those of p20(C/EBPalpha) and p20(C/EBPbeta) are increased. However, translation of 42-kDa C/EBPalpha is not down-regulated on polysomes, suggesting that aging may affect its nuclear translocation. Furthermore, recovery of the C/EBPalpha- and C/EBPbeta-binding activities and pool levels from an LPS challenge is delayed significantly in aged mouse livers. Thus, aged livers have altered steady-state levels of C/EBPalpha and C/EBPbeta isoforms. This result suggests that normal aging liver exhibits characteristics of chronic stress and a severe inability to recover from an inflammatory challenge.

Two alternative promoters direct neuron-specific expression of the rat microtubule-associated protein 1B gene

Microtubule-associated protein 1B (MAP1B) is a major constituent of the neuronal cytoskeleton that is expressed at high levels during early brain development and plays a role in axonal growth and neuronal plasticity. Previous studies suggested that the regulation of its gene expression is primarily at the transcriptional level. Thus, the characterization of the promoter region should help to define regulatory elements that control neuron-specific and developmental expression of the MAP1B gene. We have isolated genomic clones containing up to 11 kb of the upstream region of the rat MAP1B gene, sequenced approximately 1.8 kb upstream from the translation start codon, and identified several consensus sequences. These sequences include a consensus element common to several neuronal genes, a TCC repeat, a cAMP response element, and two TATA boxes that were 134 nucleotides apart from each other. S1 nuclease and RNase protection assays identified two corresponding groups of transcription initiation sites that were used selectively in distinct regions of the nervous system and during different stages of development. Transient transfection assays with neuronal and non-neuronal cell lines demonstrated that each TATA sequence and its corresponding adjacent region could independently direct neuron-specific expression of a reporter gene. Furthermore, the transcription of the reporter gene was initiated from the same sites as those of the MAP1B gene in vivo. These results suggest that two alternative and overlapping promoters, one inducible and the other constitutive, regulate the temporal and tissue-specific expression of the rat MAP1B gene.

Molecular analysis of the differential hepatic expression of rat kininogen family genes

Serum concentration of rat T1 kininogen increases 20- to 30-fold in response to acute inflammation, an induced hepatic synthesis regulated primarily at the transcriptional level. We have demonstrated by transient transfection analyses that rat T1 kininogen gene/chloramphenicol acetyltransferase (T1K/CAT) constructs are highly responsive to interleukin-6 and dexamethasone. In these studies we examined the regulation of a highly homologous K kininogen gene promoter and showed that it is minimally induced under identical conditions. The basal expression of the KK/CAT construct was, however, five- to sevenfold higher than that of the analogous T1K/CAT construct. Promoter-swapping experiments to examine the molecular basis of this differentially regulated basal expression showed that at least two K kininogen promoter regions are important for conferring its high basal expression: a distal 19-bp region (C box) constituted a binding site for C/EBP family proteins, and a proximal 66-bp region contained two adjacent binding sites for hepatocyte nuclear factor 3 (HNF-3). While the C box in the K kininogen promoter was able to interact with C/EBP transcription factors, the T1 kininogen promoter C box could not. In addition, HNF-3 binding sites of the K kininogen promoter demonstrated stronger affinities than those of the T1 kininogen promoter. Since C/EBP and HNF-3 are highly enriched in the liver and are known to enhance transcription of liver-specific genes, these differences in their binding activities thus accounted for the K kininogen gene's higher basal expression. Our studies demonstrated that evolutionary divergence of a few critical nucleotides may lead to subtle changes in the binding affinities of a transcription factor to its recognition site, profoundly altering expression of the downstream gene.

Molecular analysis of the differential hepatic expression of rat kininogen family genes

Serum concentration of rat T1 kininogen increases 20- to 30-fold in response to acute inflammation, an induced hepatic synthesis regulated primarily at the transcriptional level. We have demonstrated by transient transfection analyses that rat T1 kininogen gene/chloramphenicol acetyltransferase (T1K/CAT) constructs are highly responsive to interleukin-6 and dexamethasone. In these studies we examined the regulation of a highly homologous K kininogen gene promoter and showed that it is minimally induced under identical conditions. The basal expression of the KK/CAT construct was, however, five- to sevenfold higher than that of the analogous T1K/CAT construct. Promoter-swapping experiments to examine the molecular basis of this differentially regulated basal expression showed that at least two K kininogen promoter regions are important for conferring its high basal expression: a distal 19-bp region (C box) constituted a binding site for C/EBP family proteins, and a proximal 66-bp region contained two adjacent binding sites for hepatocyte nuclear factor 3 (HNF-3). While the C box in the K kininogen promoter was able to interact with C/EBP transcription factors, the T1 kininogen promoter C box could not. In addition, HNF-3 binding sites of the K kininogen promoter demonstrated stronger affinities than those of the T1 kininogen promoter. Since C/EBP and HNF-3 are highly enriched in the liver and are known to enhance transcription of liver-specific genes, these differences in their binding activities thus accounted for the K kininogen gene's higher basal expression. Our studies demonstrated that evolutionary divergence of a few critical nucleotides may lead to subtle changes in the binding affinities of a transcription factor to its recognition site, profoundly altering expression of the downstream gene.

Functional characterization of the promoter of pp63, a gene encoding a natural inhibitor of the insulin receptor tyrosine kinase

PP63 is a liver specific phosphorylated glycoprotein encoded by a single copy gene, which has the property of inhibiting both autophosphorylation and tyrosine kinase activity of the insulin receptor. In this study, we have analyzed the structure activity relationship of the pp63 gene promoter. Five protein binding sites were found in the proximal 5' flanking region of the gene (-223 to +4). Using oligonucleotides as competitors and purified recombinant C/EBP in footprinting and gel retardation assays, we identified two typical C/EBP sites (X1 and X3) plus a heterogenous, C/EBP-NF1 like site (X5), separated by two classical NF1 binding sites (X2 and X4). C/EBP or the related proteins were predominantly involved in supporting cell-free transcription. Occupancy of the first high affinity C/EBP site conferred almost maximal promoter efficiency, in vitro. However, this pp63 promoter activity remained very low as compared to that in intact hepatocytes. In these cells, occupancy of the first C/EBP (X1) and NF1 (X2) sites was already required for achieving a weak transcriptional activity. The use of the second C/EBP site (X3) strongly enhanced transcription, up to 60-70% of the maximum, whereas occupancy of the two more distal sites (X4 and X5) was necessary to fully activate the promoter. Thus, the strength of the promoter as well as the liver specific expression of pp63 gene appear to result from the interplay of several DNA-protein complexes involving mainly C/EBP and/or related proteins as well as the ubiquitous NF1 factor(s), rather than from the interaction of a more liver specific trans-acting factor with the promoter.