F.M.A. van Schaik

The human insulin-like growth factor II gene contains two development-specific promoters

The insulin‐like growth factors (IGF) play an important role in fetal and postnatal development. Recently, the nucleotide sequences of the cDNAs encoding IGF‐I and IGF‐II and part of the human IGF genes were reported. In this communication we describe two distinct IGF‐II cDNAs isolated from a human adult liver and a human hepatoma cDNA library, respectively. Using these two cDNAs, we have established that the human IGF‐II gene contains at least 7 exons. Two different IGF‐II promoters have been identified, 19 kilobases (kb) apart, which are active in a development‐specific manner. The promoter, active in the adult stage, is located only 1.4 kb downstream from the insulin gene.

Initial characterization of the four promoters of the human insulin-like growth factor II gene

The human insulin-like growth factor II (IGF-II) gene contains four promoters (P1-P4), which are expressed in a tissue-specific and development-dependent way. Analysis of IGF-II mRNAs in different tissues has revealed that promoters P3 and P4 are expressed in all fetal and in nonhepatic adult tissues. In adult liver, however, the promoters P2, P3 and P4 are completely shut off and another promoter, P1, is activated. To obtain more insight in the mechanisms involved in the regulation of IGF-II gene expression we have performed an initial characterization of the IGF-II promoters employing transient expression of IGF-II promoter constructs in Hep3B and HeLa cells. These studies have revealed that promoters P1, P3 and P4 are active in both cell lines tested, while no activity of promoter P2 could be detected. Employing gel retardation and DNaseI footprint analysis we have identified in the three IGF-II promoters a number of elements which are bound by nuclear proteins.

Organization of the human genes for insulin-like growth factors I and II

Recently, we have reported the isolation of cDNAs encoding the precursors of insulin‐like growth factors I and II (IGF‐I and II) [(1983) Nature 306, 609‐611; (1985) FEBS Lett. 179, 243‐246. These cDNAs were employed as specific probes to detect and isolate the corresponding genes from human cosmid DNA libraries. Three cosmids were detected, together containing the entire cDNA sequence of IGF‐I, and one cosmid containing the sequence of IGF‐II cDNA. Southern blot hybridization, physical mapping and nucleotide sequence analysis of these cosmids revealed that the IGF‐I and ‐II genes have a discontinous structure. The IGF‐I gene contains at least four exons spanning a region of probably more that 45 kilobasepairs (kb), while the IGF‐II gene consists of at least five exons, spanning a region of 16 kb.

The human IGF-I gene contains two cell type-specifically regulated promoters

The human insulin-like growth factor-I (IGF-I) gene contains two alternative leader exons: exons 1 and 2. We have identified, by transient transfection experiments, the putative promoters P1 and P2 upstream of these leader exons. The promoter regions were cloned in front of the luciferase reporter gene and their promoter activities were measured in transfected SK-N-MC (human neuroepithelioma) and OVCAR-3 (human ovarian carcinoma) cells. Both of these cell lines express the IGF-I gene endogenously, resulting in normally sized IGF-I mRNAs of 7.6, 1.3 and 1.1 kb. In SK-N-MC cells, in which P1 is the most active IGF-I promoter, P2 displayed a three times lower promoter activity than P1. However, in OVCAR-3 cells, P2 is four times more active than P1, resulting in an overall 12-fold difference in the relative promoter activities of the two IGF-I gene promoters in these two cell types. This indicates that the IGF-I promoters show a cell type-specific expression pattern.

Association between high dietary intake of the n-3 polyunsaturated fatty acid docosahexaenoic acid and reduced risk of Crohn's disease

There are plausible mechanisms for how dietary docosahexaenoic acid (DHA), an n−3 polyunsaturated fatty acid, could prevent Crohns disease (CD).

Structure and function of adenovirus DNA binding protein: comparison of the amino acid sequences of the Ad5 and Ad12 proteins derived from the nucleotide sequence of the corresponding genes.

The adenoviral DNA binding protein (DBP) is a multifunctional protein involved in DNA replication and gene expression. In order to investigate the relation between structure and function of DBP, the amino acid sequences of the serotypes 5 and 12 (Ad5 and Ad12) have been compared. The amino acid sequence of Ad5 DBP was previously established by nucleotide sequence analysis of the Ad5 DBP gene (W. Kruijer, F. M. A. Van Schaik, and J. S. Sussenbach, Nucl. Acids Res. 9, 4439-4457, 1981). In this study the analysis of the Ad5 DBP gene and adjacent regions by determination of the sequence of the first leader in late DBP mRNAs and the splice point between the tripartite leader and the main body of the mRNA encoding the 100-kDa protein has been extended. The nucleotide sequence of the Ad12 DBP gene is also described. From the nucleotide sequence and RNA mapping data of Ad12 DBP mRNAs (I. Saito, J. Sato H. Handa, K. Shiraki, and H. Shimojo, Virology 114, 379-398, 1981) the complete Ad12 DBP amino acid sequence could be deduced. Ad12 DBP contains 484 amino acids and has an actual Mr of 54,992. It is 45 amino acids shorter than Ad5 DBP. Comparison of the Ad12 and Ad5 DBP amino acid sequences shows that several longer deletions are present in the N-terminal 125 amino acid residues of Ad12 DBP. In contrast, only a single amino acid deletion and insertion is found in the C-terminal 359 amino acids of Ad12 DBP. The N- and C-terminal domains of Ad12 and Ad5 DBP are 45 and 80% homologous, respectively. This suggests that both domains of DBP are subjected to different evolutionary pressures. Analysis of various Ad5 mutants with an altered DBP gene, has indicated that the C-terminal domain is involved in DNA replication and early gene expression, while the N-terminal domain has a role in late gene expression in monkey cells. These results are discussed in relation to the structure and function of adenovirus DBP.

No association of alcohol use and the risk of ulcerative colitis or Crohn's disease: Data from a European Prospective cohort study (EPIC)

Background/Objectives:The role of long-term alcohol consumption for the risk of developing ulcerative colitis (UC) and Crohn’s disease (CD) is unclear. For the first time, to prospectively assess the role of pre-disease alcohol consumption on the risk of developing UC or CD.Subjects/Methods:Nested within the European Prospective Investigation into Cancer and Nutrition (EPIC-IBD), incident UC and CD cases and matched controls where included. At recruitment, participants completed validated food frequency and lifestyle questionnaires. Alcohol consumption was classified as either: non-use, former, light (⩽0.5 and 1 drink per week), below the recommended limits (BRL) (⩽1 and 2 drinks per day), moderate (⩽2.5 and 5 drinks per day), or heavy use (>2.5 and >5 drinks per day) for women and men, respectively; and was expressed as consumption at enrolment and during lifetime. Conditional logistic regression was applied adjusting for smoking and education, taking light users as the reference.Results:Out of 262 451 participants in six countries, 198 UC incident cases/792 controls and 84 CD cases/336 controls were included. At enrolment, 8%/27%/32%/23%/11% UC cases and 7%/29%/40%/19%/5% CD cases were: non-users, light, BRL, moderate and heavy users, respectively. The corresponding figures for lifetime non-use, former, light, BRL, moderate and heavy use were: 3%/5%/23%/44%/19%/6% and 5%/2%/25%/44%/23%/1% for UC and CD cases, respectively. There were no associations between any categories of alcohol consumption and risk of UC or CD in the unadjusted and adjusted odds ratios.Conclusion:There was no evidence of associations between alcohol use and the odds of developing either UC or CD.

Molecular aspects of the human somatomedins.

The primary structure of the somatomedins (SM) IGF-I and IGF-II has been known for some years. Both from isolation of the SMs from plasma and from the study of cDNAs it has become evident that there are more SMs, needing further study. In plasma the SMs are present in larger molecules of two size-classes: 150 kD and 40 kD, behaving as specific SM-binding proteins. The possibility that such protein classes are heterogeneous and also contain precursor molecules undergoing proteolytic processing is considered. The somatomedin genes are discontinuous and span large regions of the human genome.

Erratum : No association of alcohol use and the risk of ulcerative colitis or Crohn's disease: Data from a European Prospective cohort study (EPIC) (European Journal of Clinical Nutrition (2017) 71 (512-518) DOI: 10.1038/ejcn.2016.271)

Correction to: European Journal of Clinical Nutrition advance online publication 25 January 2017; doi:10.1038/ejcn.2016.271 Since the publication of this article, the authors have noticed an error in author affiliation 1. The correct affiliation is: Department of Epidemiology, German Institute of Human Nutrition, Potsdam, Germany.

Human insulin-like growth factors I and II (IGF-I, IGF-II) are synthesized as precursors

In an attempt to further investigate the structure of the Somatomedins/Insulin-like Growth Factors (SM/IGF), especially the possible existence of precursor peptides and their structural relation to the circulating forms, we have used recombinant-DNA techniques to identify and isolate cDNA-clones encoding human IGF-I and -II.By screening an adult human liver cDNA-library with a synthetic oligonucleotide, we initially isolated a cDNA encoding the 70 amino acids of IGF-I preceded by an N-terminal peptide of at least 25 amino acids and a carboxyl-terminal peptide of 35 amino acids, thus demonstrating that IGF-I is synthesized as a precursor. Subsequently, by cross-hybridizing the cDNA-library with restriction fragments of this cDNA we were able to isolate another cDNA clone, encoding the 67 amino acids of IGF-II, flanked by nucleotide sequences encoding a highly hydrophobic leader peptide and a carboxyl-terminal peptide.These results provide solid evidence that both IGF-I and IGF-II are synthesized as precursor proteins and that formation of IGF-I and IGF-II from these precursors requires proteolytic processing at both the N-terminal and the C-terminal ends.