Interactions of HIPPI, a molecular partner of Huntingtin interacting protein HIP1, with the specific motif present at the putative promoter sequence of the caspase-1, caspase-8 and caspase-10 genes

Proteome balance in ciliopathies: the OFD1 protein example

The balance of protein synthesis and degradation is finely regulated and influences cellular homeostasis and biological processes (e.g., embryonic development and neuronal plasticity). Recent data demonstrated that centrosomal/ciliary proteins enable proteome control in response to spatial or microenvironmental stimuli. Here, we discuss recent discoveries regarding the role in the balance of the proteome of centrosomal/ciliary proteins associated with genetic disorders known as ciliopathies. In particular, OFD1 was the first example of a ciliopathy protein controlling both protein expression and autophagic/proteasomal degradation. Understanding the role of proteome balance in the pathogenesis of the clinical manifestations of ciliopathies may pave the way to the identification of a wide range of putative novel therapeutic targets for these conditions.

Huntington's Chorea-a Rare Neurodegenerative Autosomal Dominant Disease: Insight into Molecular Genetics, Prognosis and Diagnosis

Huntington's disease is a neurodegenerative autosomal disease results due to expansion of polymorphic CAG repeats in the huntingtin gene. Phosphorylation of the translation initiation factor 4E-BP results in the alteration of the translation control leading to unwanted protein synthesis and neuronal function. Consequences of mutant huntington (mhtt) gene transcription are not well known. Variability of age of onset is an important factor of Huntington's disease separating adult and juvenile types. The factors which are taken into account are-genetic modifiers, maternal protection i.e excessive paternal transmission, superior ageing genes and environmental threshold. A major focus has been given to the molecular pathogenesis which includes-motor disturbance, cognitive disturbance and neuropsychiatric disturbance. The diagnosis part has also been taken care of. This includes genetic testing and both primary and secondary symptoms. The present review also focuses on the genetics and pathology of Huntington's disease.

Silencing HIPPI Suppresses Tumor Progression in Non-Small-Cell Lung Cancer by Inhibiting DNA Replication

Introduction

Non-small cell lung cancer (NSCLC) is the most common form of lung cancer, accounting for approximately 80%-85% of all cases of lung cancer. Huntingtin interacting protein-1 interacting protein (HIPPI) is a transcription regulator and plays an important role in apoptotic cell death. However, the role of HIPPI in NSCLC remains unclear.

Methods

Immunohistochemistry (IHC) and qRT-PCR were performed for expression analysis. The roles of HIPPI were studied using cell counting kit-8 (CCK-8), colony formation, flow cytometry, wound healing, Transwell invasion assays and mouse xenograft model. Gene microarray analysis and bioinformatics analysis were used to identify differentially expressed genes after HIPPI silencing.

Results

HIPPI is highly expressed in NSCLC tissues relative to adjacent normal tissues. Targeting HIPPI by RNA interference inhibits NSCLC cell proliferation in vitro and tumor growth in vivo. HIPPI silencing also attenuates cell migration and invasion and enhances cisplatin sensitivity in NSCLC cells. Mechanistic investigation suggests that HIPPI can positively regulate the expression of MCM2, MCM6 and MCM8, which are key regulators of DNA replication. Furthermore, consistent with HIPPI, MCM2, MCM6 and MCM8 are also upregulated in NSCLC tissues.

Conclusion

Our study highlights the importance of HIPPI for tumor biology in NSCLC and suggests that HIPPI may be a potential therapeutic target for NSCLC treatment.

Genome wide gene expression regulation by HIP1 Protein Interactor, HIPPI: prediction and validation

Background

HIP1 Protein Interactor (HIPPI) is a pro-apoptotic protein that induces Caspase8 mediated apoptosis in cell. We have shown earlier that HIPPI could interact with a specific 9 bp sequence motif, defined as the HIPPI binding site (HBS), present in the upstream promoter of Caspase1 gene and regulate its expression. We also have shown that HIPPI, without any known nuclear localization signal, could be transported to the nucleus by HIP1, a NLS containing nucleo-cytoplasmic shuttling protein. Thus our present work aims at the investigation of the role of HIPPI as a global transcription regulator.

Results

We carried out genome wide search for the presence of HBS in the upstream sequences of genes. Our result suggests that HBS was predominantly located within 2 Kb upstream from transcription start site. Transcription factors like CREBP1, TBP, OCT1, EVI1 and P53 half site were significantly enriched in the 100 bp vicinity of HBS indicating that they might co-operate with HIPPI for transcription regulation. To illustrate the role of HIPPI on transcriptome, we performed gene expression profiling by microarray. Exogenous expression of HIPPI in HeLa cells resulted in up-regulation of 580 genes (p < 0.05) while 457 genes were down-regulated. Several transcription factors including CBP, REST, C/EBP beta were altered by HIPPI in this study. HIPPI also interacted with P53 in the protein level. This interaction occurred exclusively in the nuclear compartment and was absent in cells where HIP1 was knocked down. HIPPI-P53 interaction was necessary for HIPPI mediated up-regulation of Caspase1 gene. Finally, we analyzed published microarray data obtained with post mortem brains of Huntington's disease (HD) patients to investigate the possible involvement of HIPPI in HD pathogenesis. We observed that along with the transcription factors like CREB, P300, SREBP1, Sp1 etc. which are already known to be involved in HD, HIPPI binding site was also significantly over-represented in the upstream sequences of genes altered in HD.

Conclusions

Taken together, the results suggest that HIPPI could act as an important transcription regulator in cell regulating a vast array of genes, particularly transcription factors and at least, in part, play a role in transcription deregulation observed in HD.

Regulation of RE1 protein silencing transcription factor (REST) expression by HIP1 protein interactor (HIPPI)

Earlier we have shown that the proapoptotic protein HIPPI (huntingtin interacting protein 1 (HIP1) protein interactor) along with its molecular partner HIP1 could regulate transcription of the caspase-1 gene. Here we report that RE1-silencing transcription factor/neuron-restrictive silencer factor (REST/NRSF) is a new transcriptional target of HIPPI. HIPPI could bind to the promoter of REST and increased its expression in neuronal as well as non-neuronal cells. Such activation of REST down-regulated expression of REST target genes, such as brain-derived neurotrophic factor (BDNF) or proenkephalin (PENK). The ability of HIPPI to activate REST gene transcription was dependent on HIP1, the nuclear transporter of HIPPI. Using a Huntington disease cell model, we have demonstrated that feeble interaction of HIP1 with mutant huntingtin protein resulted in increased nuclear accumulation of HIPPI and HIP1, leading to higher occupancy of HIPPI at the REST promoter, triggering its transcriptional activation and consequent repression of REST target genes. This novel transcription regulatory mechanism of REST by HIPPI may contribute to the deregulation of transcription observed in the cell model of Huntington disease.

Transcription regulation of caspase-1 by R393 of HIPPI and its molecular partner HIP-1

Earlier we have shown that exogenous expression of HIPPI, a molecular partner of Huntingtin interacting protein HIP-1, induces apoptosis and increases expression of caspases-1, -8 and -10 in HeLa and Neuro2A cells. The C-terminal pseudo death effector domain of HIPPI (pDED-HIPPI) specifically interacts with the putative promoter sequences of these genes. In the present manuscript, we predict from structural modeling of pDED-HIPPI that R393 of HIPPI is important for such interaction. R393E mutation in pDED-HIPPI decreases the interaction with the putative promoter of caspase-1 in cells. Expression of caspase-1 is decreased in cells expressing mutant pDED-HIPPI in comparison to that observed in cells expressing wild type pDED-HIPPI. Using HIP-1 knocked down cells as well as over expressing HIP-1 with mutation at its nuclear localization signal and other deletion mutations, we demonstrate that translocation of HIPPI to the nucleus is mediated by HIP-1 for the increased expression of caspase-1. HIPPI-HIP-1 heterodimer is detected in cytoplasm as well as in the nucleus and is associated with transcription complex in cells. Taking together, we are able to show the importance of R393 of HIPPI and the role of HIPPI-HIP-1 heterodimer in the transcription regulation of caspase-1.

Endocytic proteins in the regulation of nuclear signaling, transcription and tumorigenesis

Accumulating evidence argues that many proteins governing membrane sorting during endocytosis participate also in nuclear signaling and transcriptional regulation, mostly by modulating the activity of various nuclear factors. Some adaptors and accessory proteins acting in clathrin-mediated internalization, as well as endosomal sorting proteins can undergo nuclear translocation and affect gene expression directly, while for others the effects may be more indirect. Although it is often unclear to what extent the endocytic and nuclear functions are interrelated, several of such proteins are implicated in the regulation of cell proliferation and tumorigenesis, arguing that their dual-function nature may be of physiological importance.

Rybp interacts with Hippi and enhances Hippi-mediated apoptosis

Rybp (DEDAF) has been shown to interact with DED-containing proteins and to encode pro-apoptotic functions. Here we characterize a novel interaction between Rybp and Hippi, a protein implicated in neuronal apoptosis as well as in the pathogenesis of Huntington's disease. Rybp can synergize with Hippi to enhance Caspase 8-mediated apoptosis and also appears to be essential for Hippi-mediated apoptosis. Moreover, Rybp may mediate or regulate the interaction between Hippi and Caspase 8. Finally, Rybp and Hippi co-localize in a subset of neurons in the developing mouse brain. Together, these findings suggest that Rybp and Hippi may functionally interact in the apoptotic processes that accompany normal murine neural development.