A Novel Pax-like Protein Involved in Transcriptional Activation of Cyst Wall Protein Genes in Giardia lamblia

Wang, Yiting; Pan, Yu-Jiao; Cho, Chao-Cheng; Lin, Bo-Chi; Su, Li‐Hsin; Huang, Ying‐Fong; Sun, Chin-Hung

doi:10.1074/jbc.m110.156620

Cited by 23 publications

(67 citation statements)

References 77 publications

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“…We found that E2F1DB1m or E2F1DB2m with a mutation of the second Arg residue in the RRXYD motif (Fig. 7A) did not bind to the [61][62][63][64][65] and NILEG (residues 155-159) sequence. In E2F1DB1m and E2F1DB2m, the second Arg of the RRXYD DNA recognition motifs are mutated as shown in underlined type.…”

Section: Identification and Characterization Of E2f1mentioning

confidence: 93%

“…Previously, we have identified several transcription factors whose expression increased significantly during encystation and whose function may be related to the transactivation of the cwp genes, including Myb2, GARP-like protein 1, ARID1, WRKY, and Pax1 (21, 24 -27, 65). ARID1 and Pax1 can bind to the AT-rich Inr elements of the cwp promoters (24,65). Myb2, GARP-like protein 1, and WRKY can bind to the proximal upstream regions of the cwp promoters, and their binding sequences are positive cis-acting elements (21,25,27).…”

Section: Discussionmentioning

confidence: 99%

“…E2F1-binding site is closed to the AT-rich Inr element, it is more likely that there is an interaction between E2F1 and other transcription factors binding to the AT-rich Inr element, such as ARID1 and Pax1 (24,65). We further asked whether mutation of the AT-rich Inr element affects transactivation function of E2F1.…”

Section: Identification and Characterization Of E2f1mentioning

confidence: 99%

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A Novel E2F-like Protein Involved in Transcriptional Activation of Cyst Wall Protein Genes in Giardia lamblia

Pan

Huang

et al. 2011

Journal of Biological Chemistry

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Giardia lamblia differentiates into resistant walled cysts for survival outside the host and transmission. During encystation, synthesis of cyst wall proteins is coordinately induced. The E2F family of transcription factors in higher eukaryotes is involved in cell cycle progression and cell differentiation. We asked whether Giardia has E2F-like genes and whether they influence gene expression during Giardia encystation. Blast searches of the Giardia genome database identified one gene (e2f1) encoding a putative E2F protein with two putative DNA-binding domains. We found that the e2f1 gene expression levels increased significantly during encystation. Epitope-tagged E2F1 was found to localize to nuclei. Recombinant E2F1 specifically bound to the thymidine kinase and cwp1-3 gene promoters. E2F1 contains several key residues for DNA binding, and mutation analysis revealed that its binding sequence is similar to those of the known E2F family proteins. The E2F1-binding sequences were positive cis-acting elements of the thymidine kinase and cwp1 promoters. We also found that E2F1 transactivated the thymidine kinase and cwp1 promoters through its binding sequences in vivo. Interestingly, E2F1 overexpression resulted in a significant increase of the levels of CWP1 protein, cwp1-3 gene mRNA, and cyst formation. We also found E2F1 can interact with Myb2, a transcription factor that coordinate up-regulates the cwp1-3 genes during encystation. Our results suggest that E2F family has been conserved during evolution and that E2F1 is an important transcription factor in regulation of the Giardia cwp genes, which are key to Giardia differentiation into cysts.

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Section: Identification and Characterization Of E2f1mentioning

confidence: 93%

Section: Discussionmentioning

confidence: 99%

Section: Identification and Characterization Of E2f1mentioning

confidence: 99%

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A Novel E2F-like Protein Involved in Transcriptional Activation of Cyst Wall Protein Genes in Giardia lamblia

Pan

Huang

et al. 2011

Journal of Biological Chemistry

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“…Past studies and recent analysis of its genome suggested that Giardia utilizes simplified machineries for many important biological processes, ranging from DNA replication to translation initiation (Morrison et al 2007). Few consensus promoter sequences or transcription factors have been identified in Giardia (Yee et al 2007;Wang et al 2010). An 8-bp AT-rich region was shown to be sufficient to initiate transcription, which may explain the abundance of sterile transcripts in Giardia (Elmendorf et al 2001a,b).…”

Section: Introductionmentioning

confidence: 99%

A microRNA derived from an apparent canonical biogenesis pathway regulates variant surface protein gene expression in Giardia lamblia

Saraiya

Li²,

Wang³

2011

RNA

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We have previously shown that a snoRNA-derived microRNA, miR2, in Giardia lamblia potentially regulates the expression of 22 variant surface protein (VSP) genes. Here, we identified another miRNA, miR4, also capable of regulating the expression of several VSPs but derived from an unannotated open reading frame (ORF) rather than a snoRNA, suggesting a canonical miRNA biogenesis pathway in Giardia. miR4 represses expression of a reporter containing two miR4 antisense sequences at the 39 UTR without causing a corresponding decrease in the mRNA level. This repression requires the presence of the Giardia Argonaute protein (GlAgo) and is reversed by 29 O-methylated antisense oligo to miR4, suggesting an RNA-induced silencing complex (RISC)-mediated mechanism. Furthermore, in vivo and in vitro evidence suggested that the Giardia Dicer protein (GlDcr) is required for miR4 biogenesis. Coimmunoprecipitation of miR4 with GlAgo further verified miR4 as a miRNA. A total of 361 potential target sites for miR4 were bioinformatically identified in Giardia, out of which 69 (32.7%) were associated with VSP genes. miR4 reduces the expression of a reporter containing two copies of the target site from VSP (GL50803_36493) at the 39 UTR. Sixteen of the 69 VSP genes were further found to contain partially overlapping miR2 and miR4 targeting sites. Expression of a reporter carrying the two overlapping sites was inhibited by either miR2 or miR4, but the inhibition was neither synergistic nor additive, suggesting a complex mechanism of miRNA regulation of VSP expression and the presence of a rich miRNAome in Giardia.

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“…Regulation of encystment appears to be at a transcriptional level; a number of transcription factors have been characterized and shown to be involved in encystment specific gene expression (Sun et al, 2002(Sun et al, , 2006Wang et al, 2007;Huang et al, 2008;Pan et al, 2009;Wang et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

Commitment to cyst formation in Giardia

2014

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Giardia trophozoites differentiate into infectious cysts (encystment) in response to physiological stimuli; encystment is crucial for Giardia's transmission, survival and pathogenesis. In vitro, Giardia encysts when bile sequesters lipids necessary for this lipid auxotroph, and in vivo they encyst to infect new hosts. In this study, we investigated, for the first time, commitment to encystment in Giardia using both molecular and cellular techniques. We show that after 3-6 h in inducing conditions, encysting trophozoites continue to encyst regardless of whether the inducing stimulus remains. We propose that a trophozoite's inability to revert to a growing or dividing trophozoite represents a commitment to encystment. The onset of commitment correlated with the appearance of encystment specific vesicles (ESVs) and encystment specific protein synthesis. These observations suggest the involvement of regulatory pathways with the ability to 'remember' a transient signal long after its removal; a property that enables encysting trophozoites to complete the encystment process should the unfavourable triggering condition(s) change. The ability to form cysts in response to transient signals or, as we have highlighted in this paper, the ability of a small percentage of the population to form cysts without an inducer is vital for the maintenance of infection within populations.

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A Novel Pax-like Protein Involved in Transcriptional Activation of Cyst Wall Protein Genes in Giardia lamblia

Cited by 23 publications

References 77 publications

A Novel E2F-like Protein Involved in Transcriptional Activation of Cyst Wall Protein Genes in Giardia lamblia

A Novel E2F-like Protein Involved in Transcriptional Activation of Cyst Wall Protein Genes in Giardia lamblia

A microRNA derived from an apparent canonical biogenesis pathway regulates variant surface protein gene expression in Giardia lamblia

Commitment to cyst formation in Giardia

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