We have shown previously that the human cytomegalovirus (HCMV) major immediate-early (MIE) distal enhancer is needed for MIE promoter-dependent transcription and viral replication at low multiplicities of infection (MOI). To understand how this region works, we constructed and analyzed a series of HCMVs with various distal enhancer mutations. We show that the distal enhancer is composed of at least two parts that function independently to coordinately activate MIE promoter-dependent transcription and viral replication. One such part is contained in a 47-bp segment that has consensus binding sites for CREB/ATF, SP1, and YY1. At low MOI, these working parts likely function in cis to directly activate MIE gene expression, thus allowing viral replication to ensue. Three findings support the view that these working parts are likely cis-acting elements. (i) Deletion of either part of a bisegmented distal enhancer only slightly alters MIE gene transcription and viral replication. (ii) Reversing the distal enhancer's orientation largely preserves MIE gene transcription and viral replication. (iii) Placement of stop codons at ؊300 or ؊345 in all reading frames does not impair MIE gene transcription and viral replication. Lastly, we show that these working parts are dispensable at high MOI, partly because of compensatory stimulation of MIE promoter activity and viral replication that is induced by a virion-associated component(s) present at a high viral particle/cell ratio. We conclude that the distal enhancer is a complex multicomponent cis-acting region that is required to augment both MIE promoterdependent transcription and HCMV replication.The human cytomegalovirus (HCMV) major immediateearly (MIE) gene products, IE1 p72 and IE2 p86, are required for initiating viral replication (10,16,21,30). Their transcription is controlled by the MIE regulatory region, which is composed of a promoter, enhancer, unique region, and modulator (reviewed in references 25 and 29). The 485-bp enhancer segment spans base positions Ϫ65 to Ϫ550 with respect to the ϩ1 start site of MIE RNAs (25). The enhancer is recognized for its vigor in reliably activating transcription from MIE promoter constructs when put into widely diverse in vitro, transfection, and transgenic animal systems (25). However, enhancer strength depends on cell type, degree of cellular differentiation, and activity of certain signal transduction pathways (25,28). This variable functioning is a result of changes in the amounts or activities of assorted cellular and viral proteins that act on the enhancer. Examples of several distinct sets of cellular transcription factors that bind to and stimulate the enhancer include NF-B/rel, CREB/ATF, AP-1, SP-1, serum response factor, ELK-1, and liganded retinoic acid receptor (7,25,28). Some of these (NF-B/rel, CREB/ATF, SP-1, and retinoic acid receptor) bind to multiple cognate sites, suggesting that they may interact cooperatively to influence enhancer function. Viral proteins pp71 and IE1 p72 can also act through cis-acting sites ...

The human cytomegalovirus (HCMV) major immediate-early (MIE) enhancer contains five functional cyclic AMP (cAMP) response elements (CRE

. We speculate that neurohormonal stimulation via this signaling cascade is a possible means for reversing HCMV silence in vivo.Persons with impaired cellular immunity risk tissue-invasive disease from reactivation of latent human cytomegalovirus (HCMV). HCMV reactivation in tissues or blood of immunocompetent patients suffering illness from another cause also occurs but usually goes unnoticed and is self-limiting. For instance, nearly one-third of patients who are critically ill or in septic shock have detectable findings of HCMV reactivation in their bloodstream (12,26,43,45,80). HCMV reactivation infection in intestinal tissues with preexisting inflammatory disease (e.g., inflammatory bowel disease) is also well described for immunocompetent patients (28,39,40,51). The precise triggering mechanisms that underlie HCMV reactivation are unknown.So far, only cells of myeloid lineage have been determined to fulfill criteria for cellular sites of HCMV latency in vivo. In healthy HCMV-seropositive persons, precursors of macrophages and dendritic cells, including CD34ϩ hematopoietic progenitor cells, carry latent HCMV genomes at a low frequency (75). The terminal differentiation of these cells into a macrophage-or dendritic cell-like phenotype is a prerequisite for HCMV reactivation ex vivo (67, 76). However, this reactivation appears to be a rare event, suggesting that other, as yet unidentified factors may promote HCMV reactivation. Stimulation with tumor necrosis factor alpha (TNF-␣) or gamma interferon may promote HCMV reactivation from differentiated counterparts of monocytic-dendritic cell precursors that had been infected latently in vitro or in vivo (25,66,67,76).For both HCMV and murine CMV, viral major immediateearly (MIE) gene expression is greatly restricted or shut off during viral latency, and the productive viral life cycle cannot advance without this expression (57,74,75,78). The MIE enhancer/promoter controlling expression is regulated by the coordinated actions of multiple types of cis-acting elements (57). These elements are bound by cellular transcription factors whose functions are modulated by input supplied by the cell, the virus, and the external surrounding (57). Higher-order chromatin structure contributes to this regulation. Heterochromatin components amass on the inactive MIE enhancer/promoter in viral latency, whereas the chromatin signatures of transcriptional activity predominate at the active MIE enhancer/ promoter in acute and reactivation infections (47,67). MIE enhancer/promoter silencing is also favored by innate antiviral mechanisms that partly involve the repressive actions of nuclear ND10 domain components (e.g., hDAXX, PML, ATRX, and histone deacetylase [HDAC]) (52) but does not involve CpG methylation of the MIE enhancer/promoter (29).Quiescent HCMV infection of human NTera2/D1 cells (NT2 cells) is a tractable model system for studying the regulation of HCMV MIE enhancer/promoter reactivation (37, 54). NT2 cells share many phenotypic features with pluripotent

There is widespread agreement within the scientific and education communities that undergraduate biology curricula fall short in providing students with the quantitative and interdisciplinary problem-solving skills they need to obtain a deep understanding of biological phenomena and be prepared fully to contribute to future scientific inquiry. MathBench Biology Modules were designed to address these needs through a series of interactive, Web-based modules that can be used to supplement existing course content across the biological sciences curriculum. The effect of the modules was assessed in an introductory biology course at the University of Maryland. Over the course of the semester, students showed significant increases in quantitative skills that were independent of previous math course work. Students also showed increased comfort with solving quantitative problems, whether or not they ultimately arrived at the correct answer. A survey of spring 2009 graduates indicated that those who had experienced MathBench in their course work had a greater appreciation for the role of mathematics in modern biology than those who had not used MathBench. MathBench modules allow students from diverse educational backgrounds to hone their quantitative skills, preparing them for more complex mathematical approaches in upper-division courses.

Whole-genome duplication is believed to have played a signi¢cant role in the early evolution and diversi¢cation of vertebrate animals. The establishment of newly arisen polyploid lineages of sexually reproducing animals requires assortative mating between polyploids. Here, we show that genome duplication can directly alter a phenotypic trait mediating mate choice in the absence of genotypic change. Our results suggest that the direct e¡ect of polyploidy on behaviour is a consequence of increased cell size.