Conserved sequence motifs upstream from the co-ordinately expressed vitellogenin and apoVLDLII genes of chicken

Expression of Thyroid Hormone Responsive SPOT 14 Gene Is Regulated by Estrogen in Chicken (Gallus gallus)

Thyroid hormone responsive spot 14 (THRSP) is a small nuclear protein that responds rapidly to thyroid hormone. It has been shown that THRSP is abundant in lipogenic tissues such as liver, fat and the mammary gland in mammals. The THRSP gene acts as a key lipogenic activator and can be activated by thyroid hormone triiodothyronine (T3), glucose, carbohydrate and insulin. Here we report that chicken THRSP is also abundant in lipogenic tissues including the liver and the abdominal fat, and its expression levels increased with sex maturation and reached the highest level at the peak of egg production. Structure analysis of the THRSP gene indicates that there is a conscious estrogen response element (ERE) located in the −2390 – −2402 range of the gene promoter region. Further studies by ChIP-qPCR proved that the ERα interacts with the putative ERE site. In addition, THRSP was significantly upregulated (P < 0.05) when chickens or chicken primary hepatocytes were treated with 17β-estradiol in both the in vivo and in vitro conditions. We therefore conclude that THRSP is directly regulated by estrogen and is involved in the estrogen regulation network in chicken.

Chicken quantitative trait loci for growth and body composition associated with the very low density apolipoprotein-II gene

Very low density apolipoprotein-II (apoVLDL-II) is a major constituent of very low density lipoprotein and is involved in lipid transportation in chickens. The current study was designed to investigate the associations of an apoVLDL-II gene polymorphism on chicken growth and body composition traits. The Iowa Growth and Composition Resource Population was established by crossing broiler sires with dams from 2 unrelated highly inbred lines (Leghorn and Fayoumi). The F1 birds were intercrossed, within dam line, to produce 2 related F2 populations. Body weight and body composition traits were measured in the F2 population. Primers for the 5'-flanking region in apoVLDL-II were designed from database chicken genomic sequence. Single nucleotide polymorphisms (SNP) between parental lines were detected by DNA sequencing, and PCR-RFLP methods were then developed to genotype SNP in the F2 population. There was no polymorphism in the 492 bp sequenced between broiler and Leghorn. The apoVLDL-II polymorphism between broiler and Fayoumi was associated with multiple traits of growth and body composition in the 148 male F2 individuals, including BW, breast muscle weight, drumstick weight, and tibia length. This research suggests that apoVLDL-II or a tightly linked gene has broad effects on growth and development in the chicken.

Characterization of protein interactions with positive and negative elements regulating the apoVLDLII gene

Synthesis of avian apo very-low-density lipoprotein (apoVLDL)II is estrogen dependent and liver specific. Competence to express the apoVLDLII gene is not acquired until days 7-9 of embryogenesis and thus lags 5-6 days behind appearance of the liver primordial bud. It is not known whether the delayed ability to activate the gene is attributable to hepatic estrogen receptor profiles, or a requirement for other transcription factors not expressed at earlier stages of embryogenesis. The latter possibility is supported by developmental alterations in nuclease hypersensitivity flanking the gene that occur independently of estrogen administration. We have examined the influence of these hypersensitive regions on expression from the apoVLDLII promoter and have characterized novel protein-DNA interactions at two of them. One is located in a copy of the CR1 family of middle repetitive elements approximately 3.0 kb upstream from the start of the gene. We demonstrate by DNase I footprinting that the site contains an element which matches a predicted consensus silencer sequence. The other site contains no previously identified binding motifs. It is located between nucleotides -228 and -245 and is adjacent to an imperfect estrogen response element (ERE) that we demonstrate acts additively with a canonical ERE 30 nucleotides downstream. We have identified ubiquitous and liver-specific factors that display overlapping DNA contacts with the site. Mutation of G residues contacted by these proteins decreases hormone-inducible expression from the promoter 5- to 8-fold. Hepatic levels of the liver-enriched factor interacting with this site increase abruptly between days 7 and 9 of embryogenesis, suggesting that it may be an important determinant of the ability to express the apoVLDLII and possibly other liver-specific genes.

Binding of a bZip protein to the estrogen-inducible apoVLDL II promoter

Activation of the very low density apolipoprotein II (apoVLDL II) gene in chicken liver by estrogen results in the binding of a variety of nuclear proteins including members of the steroid receptor superfamily and the bZip superfamily to the immediate 5' flanking region. In the present study, we have identified a bZip protein from chicken liver as one of the potential binding activities. Its cognate cDNA was cloned from an expression library using a recognition site DNA probe corresponding to part of the apoVLDL II promoter region. By footprinting and gel shift analysis with the recombinant protein from a prokaryotic expression system we have established that the protein binds to at least three different sites in the apoVLDLII promoter region. One of these sites partially overlaps with the major estrogen response element of the gene. Despite the proximity of their binding sites, the estrogen receptor and the bZip protein can bind simultaneously to the very region. Possible implications of this intimate arrangement of binding sites for the activation of the apoVLDL II promoter are discussed.

Hepatic nuclear factor 1 alpha (HNF-1 alpha) is expressed in the oviduct of hens and interacts with regulatory elements of the lysozyme gene

HNF-1 alpha is a nuclear transcriptional regulatory protein required for the expression of a variety of liver-specific genes. This factor was previously considered liver-specific but later shown to be expressed also in a few other mammalian tissues. Here we report on the occurrence of HNF-1 alpha in the avian oviduct. This finding is of particular interest because HNF-1 alpha is not expressed in female reproductive organs of mammals. The avian oviduct is the site of assembly for the avian egg and the site of tissue-specific synthesis of the major egg white proteins, such as lysozyme. We also demonstrate that the chicken lysozyme gene contains HNF-1 recognition sites within two of its important upstream regulatory elements. The presence of HNF-1 recognition elements in functionally significant regulatory sites of the lysozyme gene and high levels of HNF-1 alpha in the oviduct is a strong indication for the involvement of HNF-1 alpha in the control of the lysozyme gene and possibly other egg white protein genes in the chicken oviduct. Apparently, HNF-1 alpha performs functions in the avian oviduct that were lost upon development from birds to mammals.

Transcription of the mouse secretory protease inhibitor p12 gene is activated by the developmentally regulated positive transcription factor Sp1

We have previously shown that a trans-acting protein produced in some tissue culture cells positively control the transcriptional activity directed by the mouse p12 promoter. This nuclear protein exerts its positive activity by interacting with a regulatory sequence designated p12.A and located between the TATA and CCAAT box elements on the p12 gene promoter. Using DNase I and dimethyl sulfate methylation interference footprinting techniques coupled with gel retardation assays, we found evidence that the protein which binds to the p12.A element is the well-known transcription factor Sp1. Mutational analysis in transient transfection assays confirmed the positive activity exerted by this protein in every cell line tested. In agreement with this observation, we detected a p12.A-Sp1 binding activity in nuclear extracts prepared from all cell lines used. However, a similar binding activity could not be detected in a number of nuclear extracts prepared from normal mouse tissues. In this report, we provide the evidence that the lack of Sp1-binding activity results from the degradation of Sp1 in the kidney, liver, and pancreas of the mouse.

Transcription of the mouse secretory protease inhibitor p12 gene is activated by the developmentally regulated positive transcription factor Sp1

We have previously shown that a trans-acting protein produced in some tissue culture cells positively control the transcriptional activity directed by the mouse p12 promoter. This nuclear protein exerts its positive activity by interacting with a regulatory sequence designated p12.A and located between the TATA and CCAAT box elements on the p12 gene promoter. Using DNase I and dimethyl sulfate methylation interference footprinting techniques coupled with gel retardation assays, we found evidence that the protein which binds to the p12.A element is the well-known transcription factor Sp1. Mutational analysis in transient transfection assays confirmed the positive activity exerted by this protein in every cell line tested. In agreement with this observation, we detected a p12.A-Sp1 binding activity in nuclear extracts prepared from all cell lines used. However, a similar binding activity could not be detected in a number of nuclear extracts prepared from normal mouse tissues. In this report, we provide the evidence that the lack of Sp1-binding activity results from the degradation of Sp1 in the kidney, liver, and pancreas of the mouse.

Presence of Vi-transposon-like elements in the proopiomelanocortin gene A of Xenopus laevis does not affect gene activity

Restriction mapping of the two proopiomelanocortin (POMC) genes of the South African clawed toad Xenopus laevis revealed that POMC gene A is much larger than POMC gene B. Here we report that this size difference is mainly due to the presence of four vitellogenin (Vi)-transposon-like elements in POMC gene A, while Vi elements are absent from POMC gene B. Alignment of these elements with other Vi elements revealed a consensus sequence of 463 bp, which is bounded by a 16 bp inverted repeat and flanked by a 3 bp direct repeat. Since the amounts of mRNA produced by both POMC genes in the pars intermedia of the Xenopus pituitary are similar, the presence of the Vi-transposon-like elements in POMC gene A apparently has no effect on POMC gene expression at transcriptional or post-transcriptional levels.

Oestrogen facilitates the binding of ubiquitous and liver-enriched nuclear proteins to the apoVLDL II promoter in vivo

Using genomic and in vitro DNasel footprinting, we have analyzed protein-DNA interactions within the promoter region of the oestrogen-inducible gene encoding chicken apoVLDL II. The footprints coincide with previously detected guanosine-protein contacts in vivo. All footprints identified are present in the apoVLDL II-expressing liver exclusively and absent in hormone-naive liver, spleen and oviduct. They comprise recognition sites for the oestrogen receptor, the ubiquitous COUP-transcription factor, the liver-enriched C/EBP and/or DBP and the liver-specific LF-A1. In vitro, binding of protein to the oestrogen response element (ERE) is excluded by the prior binding of a protein, possibly C/EBP or DBP, to an adjacent element. The recognition sequence of the COUP-TF is also a target for LF-A1. The results suggests that oestrogen-dependent liver specific activation of the apoVLDL II promoter is established by the binding of the oestrogen receptor to EREs and multiple liver-enriched factors (C/EBP, DBP and LF-A1) to their nearby recognition sequences. Apparently, several DNA binding nuclear proteins cooperate to keep the promoter in a state that is accessible for the RNA polymerase complex.

The major and minor chicken vitellogenin genes are each adjacent to partially deleted pseudogene copies of the other

The major chicken vitellogenin gene (VTGII) has previously been cloned and sequenced. We now report the isolation of genomic clones that encompass a minor chicken vitellogenin gene (VTGIII) which is also expressed in the liver in response to estradiol. Our analysis reveals that a pseudogene for VTGII (psi VTGII) lies 1,426 base pairs upstream of this VTGIII gene. A reevaluation of published sequence data reveals that the converse is also true, namely, that a pseudogene for VTGIII (psi VTGIII) lies 1,345 base pairs downstream of the VTGII gene. Our results show that a 335-base-pair deletion has removed the psi VTGIII promoter and cap site but left residual estrogen response element in a region where nuclease-hypersensitive sites have been reported to be induced in response to estradiol.

The major and minor chicken vitellogenin genes are each adjacent to partially deleted pseudogene copies of the other

The major chicken vitellogenin gene (VTGII) has previously been cloned and sequenced. We now report the isolation of genomic clones that encompass a minor chicken vitellogenin gene (VTGIII) which is also expressed in the liver in response to estradiol. Our analysis reveals that a pseudogene for VTGII (psi VTGII) lies 1,426 base pairs upstream of this VTGIII gene. A reevaluation of published sequence data reveals that the converse is also true, namely, that a pseudogene for VTGIII (psi VTGIII) lies 1,345 base pairs downstream of the VTGII gene. Our results show that a 335-base-pair deletion has removed the psi VTGIII promoter and cap site but left residual estrogen response element in a region where nuclease-hypersensitive sites have been reported to be induced in response to estradiol.

In vivo footprinting of the estrogen-inducible vitellogenin II gene from chicken

Protein-DNA interactions in the promoter region of the chicken vitellogenin II gene were analyzed by in vivo dimethylsulphate footprinting with expressing and non-expressing tissues. The reactivity of G-residues is essentially the same in erythrocytes, oviduct and control liver, not expressing the gene. In the expressing estrogen-induced liver we find a number of G-residues with altered reactivities. These G's are located within distinct sequences: the estrogen responsive elements, a sequence resembling the NF-1 recognition motive, and several elements which are conserved between yolk protein genes. The expression-dependent binding of proteins to these sites was confirmed by DNaseI footprinting applied to nuclei isolated from estrogen-induced and control liver. Estradiol appears to establish a transcription complex comprising a number of distinct proteins bound to different sites in the 5' flanking region of the vitellogenin II gene.

Two functional estrogen response elements are located upstream of the major chicken vitellogenin gene

We used a transient-expression assay to identify two estrogen response elements (EREs) associated with the major chicken vitellogenin gene (VTGII). Each element was characterized by its ability to confer estrogen responsiveness when cloned in either orientation next to a chimeric reporter gene consisting of the herpes simplex virus thymidine kinase promoter and the chloramphenicol acetyl transferase-coding region. Deletion analyses indicated that sequences necessary for the distal ERE resided within the region from -626 to -613 (nucleotide positions relative to the VTGII start site) whereas those necessary for the proximal ERE were within the region from -358 to -335. These distal and proximal elements contain, respectively, a perfect copy and an imperfect copy of the 13-base-pair sequence that is an essential feature of the EREs associated with two frog vitellogenin genes. These chicken VTGII EREs mapped near regions that were restructured at the chromatin level when the endogenous VTGII gene was expressed in the liver in response to estradiol. These data suggest a model for the tissue-specific expression of this estrogen-responsive gene.

Two functional estrogen response elements are located upstream of the major chicken vitellogenin gene

We used a transient-expression assay to identify two estrogen response elements (EREs) associated with the major chicken vitellogenin gene (VTGII). Each element was characterized by its ability to confer estrogen responsiveness when cloned in either orientation next to a chimeric reporter gene consisting of the herpes simplex virus thymidine kinase promoter and the chloramphenicol acetyl transferase-coding region. Deletion analyses indicated that sequences necessary for the distal ERE resided within the region from -626 to -613 (nucleotide positions relative to the VTGII start site) whereas those necessary for the proximal ERE were within the region from -358 to -335. These distal and proximal elements contain, respectively, a perfect copy and an imperfect copy of the 13-base-pair sequence that is an essential feature of the EREs associated with two frog vitellogenin genes. These chicken VTGII EREs mapped near regions that were restructured at the chromatin level when the endogenous VTGII gene was expressed in the liver in response to estradiol. These data suggest a model for the tissue-specific expression of this estrogen-responsive gene.

Protein-DNA interactions in vitro with 5'-flanking DNA fragments from the chicken vitellogenin gene

The expression of the vitellogenin gene in the liver of oviparous animals is under strict control of estrogen. We have studied the interaction of proteins extracted from nuclei of different estrogen responsive tissues with two fragments (-728 to -470 and -625 to -470) of the upstream region of the chicken vitellogenin gene, using the gel-retardation technique. We found a complex pattern of retarded bands using nuclear extracts from laying hen liver, rooster liver and MCF-7 cells. The patterns observed display differences in the position and intensities of some of the bands, depending on the source of the extract used. The possible significance of these findings will be discussed.

Isolation of chicken vitellogenin I and III cDNAs and the developmental regulation of five estrogen-responsive genes in the embryonic liver

The isolation of cDNA clones that code for portions of the two minor chicken vitellogenin (VTG) genes (VTGI and VTGIII) is reported. These clones represent unique sequences that are expressed exclusively in the livers of estrogenized birds. In the liver of the egg-laying hen, the levels of RNAs encoding VTGI, VTGII, and VTGIII are approximately 11,000, 30,000, and 3,000 molecules per cell, respectively. We have used the newly isolated clones, as well as the yolk protein cDNAs previously available [VTGII, apolipoprotein II (apoVLDLII), and apolipoprotein B], as probes to examine several aspects of the regulation of these genes by estradiol. First, we demonstrate that the capacity of each gene to respond to estradiol is acquired between 8 and 13 days in ovo. The response of four of these genes to estradiol is diminished during late fetal development, but the responsiveness is recovered within a week after hatching. Second, we demonstrate that these genes display distinct kinetic response profiles following the addition of estradiol. Third, as has been described previously for the VTGII and apoVLDLII genes, we demonstrate that a single injection of estradiol effects a long-term reprogramming event (hepatic memory) that allows a faster onset of the rapid accumulation of both VTGI and VTGIII RNAs following a subsequent rechallenge by estradiol. Collectively, these three sets of data suggest molecular parameters that may contribute to both the coordinate and noncoordinate regulation of this set of genes by estradiol.

The developmentally regulated expression of two linked myosin heavy-chain genes

The organization of two linked chicken myosin heavy-chain (MHC) genes is described. Using probes derived from the 3' and 5' ends of the genes, chromosome walks were carried out, resulting in the isolation of a clone which encompassed the 5' end of one MHC gene and the 3' end of a different MHC gene. Further analysis showed that both genes (each approximately 25 kbp in length) are oriented head to tail and are separated by an intergenic region of 7.5 kbp. Despite extensive homologies, a transcript-specific probe for each of the genes could be prepared from the 5' untranslated regions. These probes were used to determine the transcriptional pattern for each of the genes. The data show that the gene located at the 5' end of the linkage pair is expressed during the neonatal stages of development, while the gene located at the 3' end of the pair is expressed predominantly during the embryonic stages of development.