Scaffold attachment region located in a locus targeted by hepadnavirus integration in hepatocellular carcinomas.
The role of viral integration in HBV induced hepatocellular carcinoma (HCC) is still controversial. In the WHV/woodchuck animal model, WHV integration was found to activate the N-myc2 oncogene either by enhancer insertion in proximity of the gene, or by integration in a distantly located uncoding locus, win. In addition, we have reported that N-myc2 activation also results from WHV integration in the b3n locus, located several kilobases downstream of N-myc2. In this work we report the search for function(s) of the b3n locus that might be possibly affected by WHV integration and indirectly activate N-myc2. A 0.5 kb region of the sequence of this locus exhibited unusual features, typical of scaffold/matrix attachment regions (S/MAR). Standard in vitro binding assays are commonly used to assess if a DNA fragment is a S/MAR. DNA fragments cloned from the b3n locus were tested for in vitro binding affinity for both heterologous and autologous nuclear scaffold preparations. Only the fragment spanning the region rich of S/MAR motifs was found to bind specifically nuclear scaffolds, thus demonstrating that a S/MAR element is present in the b3n locus. Based on these findings, we speculate that WHV integration might deregulate the S/MAR element and indirectly affect the expression of the N-myc2 gene located upstream of the S/MAR. Our findings also suggest that the role of HBV integration should be reconsidered, because a similar mechanism has not been investigated to date in human HCC.
Bruni
R
R
Laboratory of Virology, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.
D'Ugo
E
E
Argentini
C
C
Giuseppetti
R
R
Rapicetta
M
M
D000818:Animals; D001665:Binding Sites; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000821:virology*; D004273:DNA, Neoplasm / Q000235:genetics / Q000378:metabolism; D004279:DNA, Viral / Q000378:metabolism; D015967:Gene Expression Regulation, Viral; D016259:Genes, myc / Q000235:genetics*; D017919:Hepatitis B Virus, Woodchuck / Q000235:genetics*; D066298:In Vitro Techniques; D008113:Liver Neoplasms / Q000235:genetics / Q000821:virology*; D008114:Liver Neoplasms, Experimental / Q000235:genetics / Q000821:virology*; D008392:Marmota; D023421:Models, Animal; D016133:Polymerase Chain Reaction; D016662:Virus Integration
D004273:DNA, Neoplasm; D004279:DNA, Viral