Bromodomain testis-specific protein is a protein that in humans is encoded by the BRDT gene. It is a member of the Bromodomain and Extra-terminal motif (BET) protein family. [5] [6]
BRDT is similar to the RING3 protein family. It possesses 2 bromodomain motifs and a PEST sequence (a cluster of proline, glutamic acid, serine, and threonine residues), characteristic of proteins that undergo rapid intracellular degradation. The bromodomain is found in proteins that regulate transcription. Two transcript variants encoding the same protein have been found for this gene. [6]
The use of three different mouse models (Brdt knock-out mice, mice expressing a non-functional Brdt and mice expressing a mutated Brdt lacking its first bromodomain) showed that Brdt drives a meiotic and post-meiotic gene expression program. It also controls the genome-wide post-meiotic genome reorganization that occurs after histone hyperacetylation in elongating spermatids. [6] [7]
BET inhibitors such as JQ1 block the region of BRDT responsible for chromatin binding, and cause a reversible reduction of sperm production, sperm quality, and size of the testis in mice. [8] The mechanism of action of JQ1 could be explained by considering Brdt’s functions as a driver of testis-specific gene expression and post-meiotic chromatin reorganization. [6] [7] As BET inhibitors also inhibit other BET proteins BRD2, BRD3, and BRD4, they are likely to have effects in people beyond temporary male sterility.
Histone H4 is a protein that in humans is encoded by the HIST4H4 gene.
Tripartite motif-containing 28 (TRIM28), also known as transcriptional intermediary factor 1β (TIF1β) and KRAB-associated protein-1 (KAP1), is a protein that in humans is encoded by the TRIM28 gene.
Bromodomain-containing protein 2 is a protein that in humans is encoded by the BRD2 gene. BRD2 is part of the Bromodomain and Extra-Terminal motif (BET) protein family that also contains BRD3, BRD4, and BRDT in mammals
Histone H4 is a protein that in humans is encoded by the HIST2H4A gene.
Histone H2A type 2-C is a protein that in humans is encoded by the HIST2H2AC gene.
Histone H2B type 3-B is a protein that in humans is encoded by the HIST3H2BB gene.
Histone H2A type 1 is a protein that in humans is encoded by the HIST1H2AM gene.
Nucleosome-remodeling factor subunit BPTF is a protein that in humans is encoded by the BPTF gene.
Histone H2A type 1-B/E is a protein that in humans is encoded by the HIST1H2AE gene.
Histone H2A type 1 is a protein that in humans is encoded by the HIST1H2AK gene.
Bromodomain-containing protein 7 is a protein that in humans is encoded by the BRD7 gene.
Histone H2B type 1-A is a protein that in humans is encoded by the HIST1H2BA gene.
Protein polybromo-1 (PB1) also known as BRG1-associated factor 180 (BAF180) is a protein that in humans is encoded by the PBRM1 gene.
Calmegin, also known as CLGN, is a protein which in humans is encoded by the CLGN gene. Calmegin is also present in other animals including mice.
Bromodomain-containing protein 3 (BRD3) also known as RING3-like protein (RING3L) is a protein that in humans is encoded by the BRD3 gene. This gene was identified based on its homology to the gene encoding the RING3 (BRD2) protein, a serine/threonine kinase. The gene maps to 9q34, a region which contains several major histocompatibility complex (MHC) genes.
Histone H4 is a protein that in humans is encoded by the HIST1H4C gene.
Kelch domain-containing protein 3 is a protein that in humans is encoded by the KLHDC3 gene.
HORMA domain-containing protein 1 (HORMAD1) also known as cancer/testis antigen 46 (CT46) is a protein that in humans is encoded by the HORMAD1 gene.
Histone H1oo is a protein that in humans is encoded by the H1FOO gene.
JQ1 is a thienotriazolodiazepine and a potent inhibitor of the BET family of bromodomain proteins which include BRD2, BRD3, BRD4, and the testis-specific protein BRDT in mammals. BET inhibitors structurally similar to JQ1 are being tested in clinical trials for a variety of cancers including NUT midline carcinoma. It was developed by the James Bradner laboratory at Brigham and Women's Hospital and named after chemist Jun Qi. The chemical structure was inspired by patent of similar BET inhibitors by Mitsubishi Tanabe Pharma. Structurally it is related to benzodiazepines. While widely used in laboratory applications, JQ1 is not itself being used in human clinical trials because it has a short half life.