Identification of functional sequences in the pregenomic RNA promoter of the Banana streak virus Cavendish strain (BSV-Cav)

The promoter regions of plant pararetroviruses direct transcription of the full-length viral genome into a pregenomic RNA that is an intermediate in the replication of the virus. It serves as template for reverse transcription and as polycistronic mRNA for translation to viral proteins. We have identified functional promoter elements in the intergenic region of the Cavendish isolate of Banana streak virus (BSV-Cav), a member of the genus Badnavirus. Potential binding sites for plant transcription factors were found both upstream and downstream of the transcription start site by homology search in the PLACE database of plant cis-acting elements. The functionality of these putative cis-acting elements was tested by constructing loss-of-function and regain-of-function mutant promoters whose activity was quantified in embryogenic sugarcane suspension cells. Four regions that are important for activity of the BSV-Cav promoter were identified: the region containing an as-l-like element, the region around-141 and down to -77, containing several putative transcription factor binding sites, the region including the CAAT-box, and the leader region. The results could help explain the high BSV-Cav promoter activity that was observed previously in transgenic sugarcane plants and give more insight into the plant cell-mediated replication of the viral genome in banana streak disease. (C) 2004 Elsevier B.V. All rights reserved.

C/EBP delta and C/EBP gamma bind the CCAAT-box in the human beta-globin promoter and modulate the activity of the CACC-box binding protein, EKLF

Developmental- and tissue-specific expression of globin genes is mediated by a few key elements within the proximal promoter of each gene. DNA-binding assays previously identified NF-Y, GATA-1, C/EBP beta and C/EBP gamma as candidate regulators of beta-globin transcription via the CCAAT-box, a promoter element situated between CACC- and TATA-boxes. We have identified C/EBP delta as an additional beta-globin CCAAT-box binding protein. In reporter assays, we show that C/EBP delta can co-operate with EKLF, a CACC-box binding protein, to activate the beta-globin promoter, whereas C/EBP gamma inhibits the transcriptional activity of EKLF in this assay. (c) 2005 Elsevier B.V. All rights reserved.

MHC promoter polymorphism in grey wolves and domestic dogs

A functional immune system requires a tight control over major histocompatibility complex (MHC) gene transcription, as the abnormal MHC expression patterns of severe immunodeficiency and autoimmune diseases demonstrate. Although the regulation of MHC expression has been well documented in humans and mice, little is known in other species. In this study, we detail the level of polymorphism in wolf and dog MHC gene promoters. The promoter regions of the DRB, DQA and DQB locus were sequenced in 90 wolves and 90 dogs. The level of polymorphism was high in the DQB promoters, with variation found within functionally relevant regions, including binding sites for transcription factors. Clear associations between DQB promoters and exon 2 alleles were noted in wolves, indicating strong linkage disequilibrium in this region. Low levels of polymorphism were found within the DRB and DQA promoter regions. However, a variable site was identified within the T box, a TNF-alpha response element, of the DQA promoter. Furthermore, we identified a previously unrecognised 18-base-pair deletion within exon 1 of the DQB locus.