A novel transcriptional repressor, Rhit, is involved in heat-inducible and age-dependent expression of Mpv17-like protein, a participant in reactive oxygen species metabolism

Transcriptomic and Functional Analyses of Two Cadmium Hyper-Enriched Duckweed Strains Reveal Putative Cadmium Tolerance Mechanisms

Cadmium (Cd) is one of the most toxic metals in the environment and exerts deleterious effects on plant growth and production. Duckweed has been reported as a promising candidate for Cd phytoremediation. In this study, the growth, Cd enrichment, and antioxidant enzyme activity of duckweed were investigated. We found that both high-Cd-tolerance duckweed (HCD) and low-Cd-tolerance duckweed (LCD) strains exposed to Cd were hyper-enriched with Cd. To further explore the underlying molecular mechanisms, a genome-wide transcriptome analysis was performed. The results showed that the growth rate, chlorophyll content, and antioxidant enzyme activities of duckweed were significantly affected by Cd stress and differed between the two strains. In the genome-wide transcriptome analysis, the RNA-seq library generated 544,347,670 clean reads, and 1608 and 2045 differentially expressed genes were identified between HCD and LCD, respectively. The antioxidant system was significantly expressed during ribosomal biosynthesis in HCD but not in LCD. Fatty acid metabolism and ethanol production were significantly increased in LCD. Alpha-linolenic acid metabolism likely plays an important role in Cd detoxification in duckweed. These findings contribute to the understanding of Cd tolerance mechanisms in hyperaccumulator plants and lay the foundation for future phytoremediation studies.

Knockout of Mpv17-Like Protein (M-LPH) Gene in Human Hepatoma Cells Results in Impairment of mtDNA Integrity through Reduction of TFAM, OGG1, and LIG3 at the Protein Levels

Human Mpv17-like protein (M-LPH) has been suggested to participate in prevention of mitochondrial dysfunction caused by mitochondrial DNA (mtDNA) damage. To clarify the molecular mechanism of M-LPH function, we knocked out M-LPH in human hepatoma HepG2 using CRISPR-Cas9 technology. An increase in mtDNA damage in M-LPH-KO HepG2 cells was demonstrated by PCR-based quantitation and 8-hydroxy-2′-deoxyguanosine (8-OHdG) measurement. Furthermore, confocal immunofluorescence analysis and Western blot analysis of mitochondrial extracts demonstrated that M-LPH-KO caused reductions in the protein levels of mitochondrial transcription factor A (TFAM), an essential factor for transcription and maintenance of mtDNA, and two DNA repair enzymes, 8-oxoguanine DNA glycosylase (OGG1) and DNA ligase 3 (LIG3), both involved in mitochondrial base excision repair (BER). Accordingly, it was suggested that the increase in mtDNA damage was due to a cumulative effect of mtDNA instability resulting from deficiencies of TFAM and diminished ability for BER arising from deficiencies in BER-related enzymes. These findings suggest that M-LPH could be involved in the maintenance of mtDNA, and therefore mitochondrial function, by protecting proteins essential for mtDNA stability and maintenance, in an integrated manner.

A universal mammalian vaccine cell line substrate

Using genome-wide small interfering RNA (siRNA) screens for poliovirus, influenza A virus and rotavirus, we validated the top 6 gene hits PV, RV or IAV to search for host genes that when knocked-down (KD) enhanced virus permissiveness and replication over wild type Vero cells or HEp-2 cells. The enhanced virus replication was tested for 12 viruses and ranged from 2-fold to >1000-fold. There were variations in virus-specific replication (strain differences) across the cell lines examined. Some host genes (CNTD2, COQ9, GCGR, NDUFA9, NEU2, PYCR1, SEC16G, SVOPL, ZFYVE9, and ZNF205) showed that KD resulted in enhanced virus replication. These findings advance platform-enabling vaccine technology, the creation of diagnostic cells substrates, and are informative about the host mechanisms that affect virus replication in mammalian cells.

Three Nonsynonymous Single Nucleotide Polymorphisms in the RhitH Gene Cause Reduction of the Repression Activity That Leads to Upregulation of M-LPH, a Participant in Mitochondrial Function

Human Mpv17-like protein (M-LPH) has been suggested to play a role in mitochondrial function. In this study, we identified a RhitH (human regulator of heat-induced transcription) binding site in intron 1 of the M-LPH gene. Tissue distribution analysis showed that M-LPH was specifically distributed in tissues with high mitochondrial metabolism. Functional and genetic analyses of nonsynonymous single nucleotide polymorphisms (SNPs) in the RhitH gene revealed that p.Cys461Ser, p.Thr465Ala, and p.Leu495Gln, corresponding to substitutions in the zinc fingers, cause reductions in the repression activity that lead to upregulation of M-LPH expression. The analyses also showed that the minor allele frequencies of these SNPs are extremely low in worldwide populations.

Identification of Rhit as a novel transcriptional repressor of human Mpv17-like protein with a mitigating effect on mitochondrial dysfunction, and its transcriptional regulation by FOXD3 and GABP

Mpv17-like protein (M-LP) is a protein that has been suggested to be involved in the metabolism of reactive oxygen species. To elucidate the molecular basis of M-LP expression, we recently searched for regulatory elements of M-LP and identified a novel mouse KRAB-containing protein, Rhit (regulator of heat-induced transcription), as a repressor of the transcriptional regulation of M-LP. In this study, we identified zinc-finger protein 205 as a candidate human Rhit (RhitH) and subsequently confirmed its participation in transcriptional regulation of human M-LP (M-LPH). To clarify the functions of RhitH and M-LPH, we searched for cis-regulatory elements in the promoter region of RhitH and identified two transcription factors: forkhead box D3, as a negative regulatory element, and GA-binding protein, one of the key regulators of the mitochondrial electron transport system, as a positive regulatory element. Additionally, it was demonstrated that knockdown of RhitH or overexpression of M-LPH reduces the generation of intracellular H(2)O(2) and loss of mitochondrial membrane potential caused by an inhibitor of the respiratory chain, antimycin A. These results suggest that M-LPH functions to protect cells from oxidative stress and/or initiation of the mitochondrial apoptotic cascade under stressed conditions.