Fenglan Lou

Activation of Telomerase by Human Cytomegalovirus

BACKGROUND The mechanism by which human cytomegalovirus (HCMV) stimulates oncogenesis is unclear. Because cellular immortalization and transformation require telomerase activation by expression of the telomerase reverse transcriptase (hTERT) gene, we examined the role of HCMV in telomerase activation. METHODS Normal human diploid fibroblasts (HDFs) and human malignant glioma (MG) cell lines were infected with HCMV or transfected with expression vectors encoding HCMV immediate early (IE) antigen 72 or 86. hTERT expression and promoter activity and telomerase activity were evaluated using reverse transcription-polymerase chain reaction, a luciferase reporter assay, and a telomeric repeat amplification protocol, respectively. hTERT promoter occupancy by the transcription factor Sp1, IE antigens, and histone deacetylases (HDACs) was assessed by chromatin immunoprecipitation. hTERT and IE protein expression in human primary glioblastoma multiforme (GBM) was determined immunohistochemically. All statistical tests were two-sided. RESULTS In telomerase and hTERT-negative HDFs, HCMV infection induced constitutive hTERT expression and telomerase activation. The hTERT promoter activity in HDFs and MG cell lines was statistically significantly enhanced by HCMV in a dose-dependent manner (mean luciferase activity [arbitrary units] in control HDFs and in HDFs infected with HCMV at multiplicities of infection [MOIs] of 0.1 = 6 and 521, respectively, difference = 515, 95% CI = 178 to 850; mean activity at MOI of 1 and 10 = 8828 and 59,923, respectively; P < .001 comparing control with HCMV-infected cells at all MOIs). Ectopic expression of HCMV IE-72 protein also stimulated hTERT promoter activity in HDFs. HCMV-mediated transactivation of the hTERT gene was dependent on the presence of Sp1-binding sites in the hTERT promoter and was accompanied by increases in Sp1 binding, acetylation of histone H3, and a reduction in HDAC binding at the core promoter. In specimens of GBM, HCMV IE and hTERT proteins were colocalized in malignant cells and their levels paralleled each other. CONCLUSIONS HCMV activates telomerase in both HDFs and malignant cells. These findings begin to reveal a novel mechanism by which HCMV infection may be linked to or modulate oncogenesis through telomerase activation.

Differential expression of full-length telomerase reverse transcriptase mRNA and telomerase activity between normal and malignant renal tissues

Activation of telomerase, a key event during immortalization and malignant transformation, requires expression of the telomerase reverse transcriptase (hTERT). Consistently, lack of telomerase activity and hTERT expression occurs in most normal human somatic cells. However, it has been observed that both normal and cancerous renal tissues express hTERT whereas only the latter exhibits telomerase activity. The mechanism underlying the dissociation between hTERT expression and telomerase activity is unclear. In the present study, we examined telomerase activity and alternative splicing of hTERT transcripts in renal cell carcinoma (RCC) specimens and adjacent normal tissues from 33 patients with RCC. Telomerase activity was detectable in 27 of 33 (82%) RCC samples but none in their normal counterparts. Thirty-two of 33 tumors expressed overall hTERT mRNA and 27 of them contained full-length hTERT transcripts, all with telomerase activity. Although 42% (14 of 33) of normal renal samples expressed hTERT mRNA, none of them had full-length hTERT transcripts, coinciding with lack of telomerase activity. The presence of full-length hTERT mRNA and telomerase activity was significantly associated with c-MYC induction. In tumors, absence of full-length hTERT mRNA or telomerase activity defines a subgroup of nonmetastatic, early-stage RCCs. Taken together, telomerase repression in normal renal tissues is attributed to the absence of full-length hTERT transcripts, whereas telomerase activation is achieved via induction of or switch to expression of full-length hTERT mRNA during the oncogenic process of kidneys, and associated with aggressive RCCs.

The Opposing Effect of Hypoxia-Inducible Factor-2α on Expression of Telomerase Reverse Transcriptase

Hypoxia-inducible factor-1α (HIF-1α) has been implicated in the transcriptional regulation of the telomerase reverse transcriptase (hTERT) gene expression and telomerase activity, essential elements for cellular immortalization and transformation. However, controversial results were obtained in different studies. Moreover, it is totally unclear whether HIF-2α, the paralog of HIF-1α, plays a role in regulating hTERT expression. In the present study, we found that hypoxic treatment enhanced hTERT mRNA expression and telomerase activity in three renal cell carcinoma (RCC) cell lines with different genetic backgrounds. Both HIF-1α and HIF-2α were capable of significantly increasing the hTERT promoter activity in these cells. Moreover, depleting HIF-2α led to a down-regulation of hTERT mRNA level in RCC A498 cells expressing constitutive HIF-2α. It was found that HIF-2α bound to the hTERT proximal promoter and enhanced the recruitment of the histone acetyltransferase p300 and histone H3 acetylation locally in A498 cells treated with hypoxia. Increased levels of hTERT mRNA were observed in two of three hypoxia-treated malignant glioma cell lines. However, HIF-1α stimulated whereas HIF-2α inhibited the hTERT promoter activity in these glioma cell lines. Ectopic expression of HIF-2α resulted in diminished hTERT expression in glioma cells. Collectively, HIF-1α activates hTERT and telomerase expression in both RCC and glioma cells, and HIF-2α enhances hTERT expression in RCC cells, whereas it represses the hTERT transcription in glioma cells. These findings reveal a complex relationship between HIF-1α/2α and hTERT/telomerase expression in malignant cells, which may have both biological and clinical implications. (Mol Cancer Res 2007;5(8):793–800)

Impact of Childhood Adversity and Vasopressin receptor 1a Variation on Social Interaction in Adulthood: A Cross-Sectional Study.

Background Arginine vasopressin (AVP) plays a role in social behavior, through receptor AVPR1A. The promoter polymorphism AVPR1A RS3 has been associated with human social behaviors, and with acute response to stress. Here, the relationships between AVPR1A RS3, early-life stressors, and social interaction in adulthood were explored. Methods Adult individuals from a Swedish population-based cohort (n = 1871) were assessed for self-reported availability of social integration and social attachment and for experience of childhood adversities. Their DNA samples were genotyped for the microsatellite AVPR1A RS3. Results Among males, particularly those homozygous for the long alleles of AVPR1A RS3 were vulnerable to childhood adversity for their social attachment in adulthood. A similar vulnerability to childhood adversity among long allele carriers was found on adulthood social integration, but here both males and females were influenced. Limitation Data were self-reported and childhood adversity data were retrospective. Conclusions Early-life stress influenced the relationship between AVPR1A genetic variants and social interaction. For social attachment, AVPR1A was of importance in males only. The findings add to previous reports on higher acute vulnerability to stress in persons with long AVPR1A RS3 alleles and increased AVP levels.

A survey comparing the attitudes toward perinatal bereavement care of nurses from three Asian cities.

Caring for parents whose infant has died is extremely demanding, difficult, and stressful. In some situations, nurses may experience personal failure, feel helpless, and need to distance themselves from bereaved parents because they are unable to deal with the enormity of the parental feelings of loss. The aim of the study was to describe and compare attitudes toward perinatal bereavement care across a sample of nurses working in five obstetrics and gynecology settings from three Asian cities, as well as the factors associated with these attitudes. A survey was conducted, and 573 nurses were recruited from 2006 to 2007. The data were collected using the perinatal bereavement attitudes scale, which involves an 11-item self-report questionnaire. Nurses’ attitudes were mainly positive, but differed across cities, with the attitude of Jinan nurses being significantly more positive than nurses from the other two cities, and the attitude of Hong Kong nurses being significantly the lowest. Positive attitudes were associated with position, and nurses who were well informed of hospital policy and received training for bereavement care were statistically significantly more likely to have a positive attitude toward perinatal bereavement care. Although nurses’ attitudes to prenatal bereavement care differ significantly across the three Asian cities, they are generally similar. The differences observed could be related to the wider social, cultural, and organizational circumstances of nursing practice.

Promoter polymorphism in the serotonin transporter (5-HTT) gene is significantly associated with leukocyte telomere length in Han Chinese.

The serotonin transporter gene (5-HTT)-linked polymorphic region (5-HTTLPR) plays an important role in modulating mood and behavior by regulating 5-HTT expression and thereby controlling the concentration of serotonin (5-HT) in brain synapses: The homozygous shorter allele (S/S) in 5-HTTLPR results in lower 5-HTT expression coupled with stronger psycho-pathological reactions to stressful experiences compared to the homozygous long (L/L) and heterozygous (S/L) alleles. Psychological insults and mood disorders have been shown to cause accelerated telomere shortening, a marker of biological aging, however, it is currently unclear whether the allelic variants of 5-HTTLPR affect telomere length (TL) in the healthy population without mood disorders. In the present study, we determined the relationship between TL and the 5-HTTLPR variants in healthy Han Chinese. The 5-HTTLPR genotyping and leukocyte TL analysis of 280 young female Han Chinese freshmen showed a significantly shorter TL in 149 of them carrying the 5-HTTLPR S/S version compared to those (131) with the L/S or L/S plus L/L genotypes (mean ± SD, 0.533±0.241 for S/S vs 0.607±0.312 for L/S, P  =  0.034; or vs 0.604±0.313 for L/S plus L/L, P  =  0.038). Similar results were achieved in the other cohort including 220 adult healthy individuals of different age, gender and profession (0.691±0.168 for S/S vs 0.729±0.211 for L/S, P  =  0.046, or vs 0.725±0.213 for L/S plus L/L, P  =  0.039). Taken together, shorter leukocyte TL is significantly associated with the 5-HTTLPR S/S allelic variant, which may be implicated in psychological stress-related health problems.

5-HTTLPR, victimization and ecological executive function of adolescents

Executive function (EF) plays an important role in guiding peer relationship, school performance and behavior control. Children exposed to traumatic environments have been reported to perform poorer in EF tasks. We explored if the relationship between victimization and EF was dependent on the functional variation 5-HTTLPR in a non-clinical sample of adolescents. Data on demographics, victimization and daily life EF were collected from school students (Han Chinese, n=2125). All those reporting executive dysfunction (n=169), and classmate controls (n=208), were genotyped for the 5-HTTLPR. It was shown that the number of victimizations associated positively with executive dysfunction (ED). This association was particularly strong in those homozygous for the short allele of 5-HTTLPR, whilst a statistical 5-HTTLPR×victimization interaction on ED was found. Our findings suggest that adolescents with a genotype conferring a low 5-HTT activity are more vulnerable to a childhood adversity-associated ED in their daily life.