The Identification of Prx1 Transcription Regulatory Domains Provides a Mechanism for Unequal Compensation by thePrx1 and Prx2 Loci

Norris, Russell A.; Kern, Michael J.

doi:10.1074/jbc.m100239200

Cited by 57 publications

(72 citation statements)

References 44 publications

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“…In Cart1 and in Prx proteins the aristaless domain has an inhibitory function (45). This does not seem to be the case for Alx3, because deletion of the region that contains the aristaless domain (Alx3-(1-279)) does not result in transcriptional enhancement in transfected cells, consistent with the notion that Alx3 contains a divergent aristaless domain that appears not to be functional (46).…”

Section: Proline-rich Domains Confer Transcriptional Transactivation supporting

confidence: 61%

The Homeoprotein Alx3 Contains Discrete Functional Domains and Exhibits Cell-specific and Selective Monomeric Binding and Transactivation

Pérez-Villamil

Mirasierra

Vallejo

2004

Journal of Biological Chemistry

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Alx3 is a paired class aristaless-like homeoprotein expressed during embryonic development. Transcriptional transactivation by aristaless-like proteins has been associated with cooperative dimerization upon binding to artificially generated DNA consensus sequences known as P3 sites, but natural target sites in genes regulated by Alx3 are unknown. We report the cloning of a cDNA encoding the rat homolog of Alx3, and we characterize the protein domains that are important for transactivation, dimerization, and binding to DNA. Two proline-rich domains located amino-terminal to the homeodomain (Pro1 and Pro2) are necessary for Alx3-dependent transactivation, whereas another one (Pro3) located in the carboxyl terminus is dispensable but contributes to enhance the magnitude of the response. We confirmed that transcriptional activity of Alx3 from a P3 site correlates with cooperative dimerization upon binding to DNA. However, Alx3 was found to bind selectively to non-P3-related TAAT-containing sites present in the promoter of the somatostatin gene in a specific manner that depends on the nuclear protein environment. Cell-specific transactivation elicited by Alx3 from these sites could not be predicted from in vitro DNAbinding experiments by using recombinant Alx3. In addition, transactivation did not depend on cooperative dimerization upon binding to cognate somatostatin DNA sites. Our data indicate that the paradigm according to which Alx3 must act homodimerically via cooperative binding to P3-like sites is insufficient to explain the mechanism of action of this homeoprotein to regulate transcription of natural target genes. Instead, Alx3 undergoes restrictive or permissive interactions with nuclear proteins that determine its binding to and transactivation from TAAT target sites selected in a cellspecific manner.Homeodomain proteins are a large family of transcription factors that play prominent roles during embryonic development (1, 2). These proteins are characterized by the existence of a common DNA-binding structure, known as the homeodomain, that contains three ␣-helices spanning 60 amino acids.Comparison of amino acid sequences of known homeodomains from different species shows that residues in the first and third helices are highly conserved. Thus, the relative degree of sequence similarity in the DNA-binding domain defines different classes of homeodomain proteins that relate to protein homologs encoded by Drosophila melanogaster genes (3).Among the different classes of homeoproteins categorized so far, an important group with major roles in embryonic development is that of paired class proteins, characterized by the presence of a homeodomain homologous to the one encoded by the Drosophila paired gene (4). Additional conserved regions located outside the homeodomain define different subsets of paired class transcription factors.One of these subsets of paired class homeoproteins is characterized by the presence of a conserved domain located in the carboxyl-terminal region known as OAR or aristaless domain (4, 5...

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Section: Proline-rich Domains Confer Transcriptional Transactivation supporting

confidence: 61%

The Homeoprotein Alx3 Contains Discrete Functional Domains and Exhibits Cell-specific and Selective Monomeric Binding and Transactivation

Pérez-Villamil

Mirasierra

Vallejo

2004

Journal of Biological Chemistry

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“…Continuing with this model, if the regulatory mechanism were ever rendered nonfunctional due to mutations, then it is likely that the presence of Prx1 protein may contribute to heart malformations or altered cardiac function. Prx1 is a potent activator of TN-C transcription (Norris and Kern, 2001). In at least one cardiac disease state, aortic valve stenosis, TN-C is up-regulated (Li et al, 2000).…”

Section: Prx1 Expression In the Murine And Avian Heartmentioning

confidence: 99%

Investigation of Prx1 protein expression provides evidence for conservation of cardiac‐specific posttranscriptional regulation in vertebrates

Chesterman

Gainey

Varn

et al. 2001

Developmental Dynamics

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Gene targeting experiments have defined that the homeobox gene Prx1 is essential for normal craniofacial, limb, and vascular development. Although its RNA expression pattern is well established, Prx1 protein expression in the developing embryo has not been examined. A novel Prx1 antibody was produced to define the normal Prx1 protein expression pattern in the developing mouse embryo. In craniofacial and limb mesenchyme, Prx1 protein expression is consistent with previously published data on RNA localization. However, a remarkable discrepancy was found in cardiac tissue. Prx1 protein is undetectable in the murine embryonic and adult heart, despite the presence of Prx1 transcripts. These data demonstrate that Prx1 expression is posttranscriptionally regulated. This discrepancy between the presence of Prx1 transcript and the absence of detectable protein was also observed in embryonic chick heart, suggesting conservation of the regulatory mechanism in vertebrates. This observation provides a new explanation of why the Prx null mice lack cardiac malformations.

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“…The OAR (a.k.a. aristaless) domain was shown to inhibit or mask nearby potent activation domains of Prx1a (Norris and Kern, 2001b). Natural and engineered mouse mutants of several paired-type homeoproteins with an OAR domain resulted in defects of cartilage and bone development (Zhao et al, 1996;Qu et al, 1997Qu et al, , 1998Qu et al, , 1999ten Berge et al, 1998b;Lu et al, 1999a,b;.…”

Section: Introductionmentioning

confidence: 99%

“…and E.S.C., unpublished data). Biochemical assessment of the two Prx1 isoforms in a transient cotransfection system defined that Prx1a is a transcriptional activator and Prx1b is a transcriptional repressor (Norris and Kern, 2001b). Repressor activity within the Prx1b protein was localized to the carboxy terminus, encoded within the alternatively spliced exon 4.…”

Section: Introductionmentioning

confidence: 99%

“…Cells used for in vitro micro mass cultures were isolated from chick limbs at Hamburger and Hamilton stage 22-24 chick embryos. These cells were transfected with constructs expressing Prx1a, Prx1a⌬OAR, Prx1b (Norris and Kern, 2001b) or LacZ by electroporation. Cells were plated in 10-l droplets of medium at 2 ϫ 10 5 , 1 ϫ 10 5 , or 5 ϫ 10 4 (not shown) cells in triplicate.…”

Section: Introductionmentioning

confidence: 99%

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Opposing roles of two isoforms of the Prx1 homeobox gene in chondrogenesis

Peterson

Hoffman

Kern

2005

Developmental Dynamics

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The Prx1 homeobox gene is critical for cartilage and bone development as suggested by previous expression studies and demonstrated by gene targeting. However, neither approach assessed the individual roles of the two isoforms Prx1a and Prx1b. In this study, Western blot analysis demonstrates that, in the early stages of chondrogenesis, during mesenchymal condensation, only Prx1a is expressed. Higher level Prx1b expression is concomitant with the formation of a defined perichondrium. Prx1a overexpression in limb micro mass cultures results in an increase in the number of prechondrogenic condensations and cartilage nodules, whereas overexpression of Prx1b results in a decrease. Prx1a increases the percentage of proliferating cells in micro mass cultures and decreases apoptosis. The Prx1b isoform does not alter proliferation, but it does increase apoptosis, which is opposite of Prx1a. These results suggest that the Prx1a:Prx1b ratio and the alternative splicing mechanism that generates these two isoforms are critical in controlling chondrogenesis. Developmental Dynamics 233:811-821, 2005.

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The Identification of Prx1 Transcription Regulatory Domains Provides a Mechanism for Unequal Compensation by thePrx1 and Prx2 Loci

Cited by 57 publications

References 44 publications

The Homeoprotein Alx3 Contains Discrete Functional Domains and Exhibits Cell-specific and Selective Monomeric Binding and Transactivation

The Homeoprotein Alx3 Contains Discrete Functional Domains and Exhibits Cell-specific and Selective Monomeric Binding and Transactivation

Investigation of Prx1 protein expression provides evidence for conservation of cardiac‐specific posttranscriptional regulation in vertebrates

Opposing roles of two isoforms of the Prx1 homeobox gene in chondrogenesis

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