MINOTAUR - MINing Online Text - A User-friendly Resource (UNIVERSITY OF MANCHESTER BIOINFORMATICS EDUCATION AND RESEARCH)

Investigations in mice lacking the first zinc finger of the VDR have demonstrated that they express a truncated receptor containing an intact ligand binding and AF2 domain .

These mice are a phenocopy of mice lacking the VDR , thus demonstrate the critical requirement of the DNA binding domain for hair follicle homeostasis .

Transgenic mice expressing VDRs with mutations in either the ligand-binding domain or the AF2 domain were generated .

Keratinocyte-specific expression of a VDR transgene with a mutation in the hormone-binding domain that abolishes ligand binding restores normal hair cycling in VDR null mice , whereas a VDR transgene with a mutation in the activation function 2 domain that impairs nuclear receptor coactivator recruitment results in a partial rescue .

The Hr contact site in human VDR is localized to the central portion of the ligand binding domain , a known corepressor docking region in other nuclear receptors separate from the activation function-2 domain .

Coimmunoprecipitation and functional studies of Hr deletants reveal that VDR contacts a C-terminal region of Hr that includes motifs required for TR and RORalpha binding .

Here , we show that this deletion removes the stop codon and creates a new reading frame at the C terminus of the hairless protein , generating a larger mutant protein harboring an additional sequence of 117 amino acids .

VDR functions as a hormonally activated transcription factor , and a role in transcription has been postulated for Hr due in part to its nuclear localization and homology with the GATA-1 zinc-finger domain .

The truncated VDR weakly bound [ 3H]-1,25 ( OH ) 2D3 but was able to heterodimerize with RXR , bind to DNA and interact with the corepressor hairless ( HR ) .

This activity required functional vitamin D-responsive promoter elements as well as an intact VDR DNA binding domain and thus could not be distinguished from 1,25 ( OH ) 2D3-dependent VDR transactivation .

Indeed , this 1,25 ( OH ) 2D3-independent VDR-RXR heterodimerization was sufficient to drive transactivation by VDR ( L233S ) , an inactive ligand binding mutant of VDR that was previously shown to rescue the skin phenotype of VDR null mice .

Regulation of mouse RANKL by 1,25 ( OH ) ( 2 ) D ( 3 ) supports a cloverleaf model , whereby VDR-RXR heterodimers bound to multiple VDREs are juxtapositioned through chromatin looping to form a supercomplex , potentially allowing simultaneous interactions with multiple co-modulators and chromatin remodeling enzymes .

The mutated protein is expected to contain no ligand-binding domain .

This missense mutation occurs in the vicinity of repression domain 3 of the hairless protein ( HR ) .

The genotypes were classified as FF ( absence of the FokI site ) and ff ( presence of the FokI site ) .

These receptors form RAR / RXR heterodimers , which bind to genetic regulatory DNA sequences and activate transcription of RA target genes .

As RXR form heterodimers with a number of other nuclear receptors , such as the vitamin D3 receptor ( VDR ) and are involved in several signaling pathways .

Vitamin D receptor ( VDR ) and retinoid X receptor ( RXR ) are members of the nuclear receptor superfamily and they bind target DNA sequences as heterodimers to regulate transcription .

Emerging information regarding the regulatory control of dimerization based on biochemical , structural , and genetic studies is then presented .

Finally , the main focus of this article is a new dynamic perspective of dimerization functions , based on recent research with fluorescent protein chimeras in living cells by microscopy .

It is believed that these receptors form heterodimers with retinoid X receptors ( RXRs ) to act as transcriptional regulators .