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Within this work, a new class of sequence-defined heteromultivalent glycomacromolecules bearing lactose residues and nonglycosidic motifs for probing glycoconjugate recognition in carbohydrate recognition domain (CRD) of galectin-3 is presented. Galectins, a family of β-galactoside-binding proteins, are known to play crucial roles in different signaling pathways involved in tumor biology. Thus, research has focused on the design and synthesis of galectin-targeting ligands for use as diagnostic markers or potential therapeutics. Heteromultivalent precision glycomacromolecules have the potential to serve as ligands for galectins. In this work, multivalency and the introduction of nonglycosidic motifs bearing either neutral, amine, or sulfonated/sulfated groups are used to better understand binding in the galectin-3 CRD. Enzyme-linked immunosorbent assays and surface plasmon resonance studies are performed, revealing a positive impact of the sulfonated/sulfated nonglycosidic motifs on galectin-3 binding but not on galectin-1 binding. Selected compounds are then tested with galectin-3 positive MCF 7 breast cancer cells using an in vitro would scratch assay. Preliminary results demonstrate a differential biological effect on MCF 7 cells with high galectin-3 expression in comparison to an HEK 293 control with low galectin-3 expression, indicating the potential for sulfonated/sulfated heteromultivalent glycomacromolecules to serve as preferential ligands for galectin-3 targeting., (© 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Expression of the CD4 gene is tightly controlled throughout thymopoiesis. The downregulation of CD4 gene expression in CD4(-) CD8(-) and CD4(-) CD8(+) T lymphocytes is controlled by a transcriptional silencer located in the first intron of the CD4 locus. Here, we determine that the c-Myb transcription factor binds to a functional site in the CD4 silencer. As c-Myb is also required for CD4 promoter function, these data indicate that depending on the context, c-Myb plays both positive and negative roles in the control of CD4 gene expression. Interestingly, a second CD4 silencer-binding factor, HES-1, binds to c-Myb in vivo and induces it to become a transcriptional repressor. We propose that the recruitment of HES-1 and c-Myb to the silencer leads to the formation of a multifactor complex that induces silencer function and repression of CD4 gene expression.

The control of CD4 expression is linked to the signaling events that mediate T-cell development and is directly dependent on the CD4 promoter. The CD4 promoter does not contain functionally redundant sites: all four factor-binding sites must be intact to achieve wild-type activity. Here we demonstrate that the precise position of three factor-binding sites relative to each other is essential for promoter activity, indicating that they function together as an inseparable cassette for assembly of the transcription initiation complex. Small changes in either phasing or distance between any two sites in this cassette leads to complete abrogation of promoter function. In addition, we demonstrate that one of the factors that bind the promoter cassette is not present in CD8 SP T(C) cells. Thus, this factor is a candidate for mediating the relative subclass specificity of CD4 promoter function in activated CD4 SP T(H) cells.

The control of CD4 gene expression is essential for proper T lymphocyte development. Signals transmitted from the T-cell antigen receptor (TCR) during the thymic selection processes are believed to be linked to the regulation of CD4 gene expression during specific stages of T cell development. Thus, a study of the factors that control CD4 gene expression may lead to further insight into the molecular mechanisms that drive thymic selection. In this review, we discuss the work conducted to date to identify and characterize the cis-acting transcriptional control elements in the CD4 locus and the DNA-binding factors that mediate their function. From these studies, it is becoming clear that the molecular mechanisms controlling CD4 gene expression are very complex and differ at each stage of development. Thus, the control of CD4 expression is subject to many different influences as the thymocyte develops.

The control of CD4 gene expression is believed to be linked directly to the signaling events that mediate T cell development and is directly dependent on the CD4 promoter. We have previously determined that this promoter contains four factor-binding sites important for its function. One of these sites, referred to as the P4 site, contains an Ets consensus recognition sequence. Using functional and biochemical analyses, we determine that Elf-1 binds to this site and specifically activates the CD4 promoter, indicating that Elf-1 is playing an important role in CD4 promoter function. In addition, a second nuclear factor binds to this region. Although there are consensus recognition sites for other factors, we demonstrate that none of these factors binds to the P4 site, nor do other known members of the Ets family. Thus, a novel transcription factor may bind to the CD4 promoter and help mediate its function.