Radial organization of nuclei with peripheral gene-poor chromosomes and central gene-rich chromosomes is common and could depend on the nuclear boundary as a scaffold or position marker. To test this, we studied the role of the ubiquitous nuclear envelope (NE) component lamin B1 in NE stability, chromosome territory position, and gene expression. The stability of the lamin B1 lamina is dependent on lamin endoproteolysis (by Rce1) but not carboxymethylation (by Icmt), whereas lamin C lamina stability is not affected by the loss of full-length lamin B1 or its processing. Comparison of wild-type murine fibroblasts with fibroblasts lacking full-length lamin B1, or defective in CAAX processing, identified genes that depend on a stable processed lamin B1 lamina for normal expression. We also demonstrate that the position of mouse chromosome 18 but not 19 is dependent on such a stable nuclear lamina. The results implicate processed lamin B1 in the control of gene expression as well as chromosome position.

DAS181 significantly reduced viral load in participants infected with influenza, thus warranting future clinical development of this novel host-directed therapy. CLINICAL TRIALS.GOV IDENTIFIER: NCT01037205.

The human cytomegalovirus (HCMV) IE2 86-kDa protein is an essential transactivator of viral and cellular gene expression. Additional proteins of 60 and 40 kDa are expressed from the IE2 gene at late times postinfection and are identical to the C terminus of IE2 86. We have constructed HCMV recombinants that express wild-type full-length IE2 86 but do not express the IE2 40-and 60-kDa proteins. Each of these recombinants is viable, indicating that neither the 60-kDa nor the 40-kDa protein is required for virus replication, either alone or in combination. Cells infected with the IE2 60 and IE2 40 deletion mutants, however, exhibit decreased expression of selected viral genes at late times. In particular, expression of the viral DNA replication factor UL84 is affected by the deletion of IE2 40, and expression of the tegument protein pp65 (ppUL83) is affected by the deletion of both IE2 40 and IE2 60. IE2 60 and IE2 40 are also required for the production of normal levels of infectious virus. Finally, IE2 40 appears to function as a repressor of major immediate-early transcription in the infected cell. These results begin to define functions for the IE2 60-and IE2 40-kDa proteins and indicate that these products contribute both to the expression of selected viral genes and to the overall progression of the infection.Human cytomegalovirus (HCMV) gene expression, like that of all herpesviruses, occurs as a tightly controlled series of events beginning with expression of the immediate-early (IE) genes. These go on to activate expression of early viral genes, allowing replication of the viral genome and subsequent transcription of late, primarily structural, genes. Two important IE genes, the UL122 and UL123 genes, comprise the major IE region. This segment of the HCMV genome encodes two predominant products, the IE1 72-kDa (ppUL123) and IE2 86-kDa (ppUL122) proteins. These are expressed from alternatively spliced forms of a five-exon transcript; the IE1 72 mRNA consists of exons 1 to 4, and the IE2 86 mRNA contains exons 1 to 3 and 5. Translation of both proteins begins in exon 2, so that IE1 72 and IE2 86 have identical 85-amino-acid (aa) N termini and unique C-terminal domains. Both proteins have been characterized extensively, most recently in studies that have used recombinant viruses containing deletions in the major IE region to elucidate the functions of IE1 72 and IE2 86 in the HCMV-infected cell. These studies indicate that the IE1 72-kDa protein contributes to virus replication during lowmultiplicity, but not high-multiplicity, infections and is therefore nonessential (10,11,28). In contrast, IE2 86 is strictly required for HCMV replication, and even small deletions or changes to the sequence of the protein can result in a virus that does not replicate (26,46). Both IE1 72 and IE2 86 are transcriptional activators, and their ability to promote viral gene expression has been studied in a number of transient-transfection assays. IE2 86-mediated transactivation of the 1.2-and 2.7-kb RNA and UL112-113 (2.2-kb RNA...

Diacylglycerol acyltransferase 2 (DGAT2) catalyzes the final step of triacylglycerol (TG) synthesis. Despite the existence of an alternative acyltransferase (DGAT1), mice lacking DGAT2 have a severe deficiency of TG in adipose tissue, indicating a nonredundant role for this enzyme in adipocyte TG synthesis. We have studied the regulation of DGAT2 expression during adipogenesis. In both isolated murine preadipocytes and 3T3-L1 cells the temporal pattern of DGAT2 expression closely mimicked that of genes whose expression is regulated by CAAT/enhancerbinding protein ␤ (C/EBP␤). Inhibition of C/EBP␤ expression in differentiating preadipocytes reduced DGAT2 expression, and electrophoretic mobility shift assay and chromatin immunoprecipitation experiments identified a promoter element in the DGAT2 gene that is likely to mediate this effect. The importance of C/EBP␤ in adipocyte expression of DGAT2 was confirmed by the finding of reduced DGAT2 expression in the adipose tissue of C/EBP␤-null animals. However, DGAT2 expression is maintained at high levels during the later stages of adipogenesis, when C/EBP␤ levels decline. We show that, at these later stages of differentiation, C/EBP␣ is capable of substituting for C/EBP␤ at the same promoter element. These observations provide novel insight into the transcriptional regulation of DGAT2 expression. Moreover, they further refine the complex and serial roles of the C/EBP family of transcription factors in inducing and maintaining the metabolic properties of mature adipocytes.The increased adipose tissue mass of obesity results from a combination of increased lipid storage in existing adipocytes and the generation of new adipocytes from precursors residing within the adipose tissue (1). The induction of genes responsible for the formation of triacylglycerol (TG) 3 within developing or pre-existing adipocytes is therefore likely to make an important contribution to the enlargement of adipose mass. In contrast, pathologically decreased lipid accumulation or impaired adipogenesis in lipodystrophic subjects has deleterious metabolic consequences superficially like those seen in obesity, including insulin resistance and dyslipidemia, with attendant increases in cardiovascular disease. Thus good metabolic control is likely to require the body to restrain adipose tissue mass while still maintaining the capacity to respond accurately to substrate availability. In this way, when necessary, lipids can be partitioned appropriately into adipose tissue and away from other insulin-sensitive tissues where they may have detrimental effects. That mutations of AGPAT2, a key enzyme in TG synthesis, can cause near total lipodystrophy demonstrates the importance of this pathway in such diseases of adipose development and function (2, 3). Rational therapeutic strategies for both obesity and lipodystrophy will require a detailed knowledge of the regulatory pathways required for the formation of an appropriate mass of metabolically active adipocytes, capable of tightly controlling lipid synthesis...