MAGOHB Human

What is MAGOHB and how is it related to MAGOH?

MAGOHB is a paralog of MAGOH, with both being core proteins of the Exon Junction Complex (EJC). The EJC is deposited 24 bases upstream of newly formed exon-exon junctions during splicing in eukaryotic gene expression. MAGOH and MAGOHB form heterodimers with RBM8A, another core-EJC protein. These paralogs are highly conserved across vertebrates, suggesting their evolutionary importance in RNA processing pathways . While they share significant sequence similarity, they may have both overlapping and distinct functions in cellular processes.

Where is the MAGOHB gene located in the human genome?

The human MAGOHB gene is located on the reverse strand of chromosome 12 at position 12p13.2 (chr12:10,604,193-10,613,609, GRCh38/hg38) . This genomic location is important for researchers designing primers for genomic analysis or considering positional effects on gene regulation. In contrast, its paralog MAGOH is located on a different chromosome, allowing for independent regulation despite their functional similarities.

What are the known isoforms of MAGOHB and their structural differences?

According to the Ensembl genome browser data, human MAGOHB pre-mRNA generates eleven alternately spliced transcripts, of which three have coding potential. The two major protein-coding transcripts are:

• MAGOHB-201: The primary transcript, containing five exons and coding for the 148 amino acid principal protein isoform.

• MAGOHB-204: An alternate transcript coding for a 102 amino acid protein isoform.

These transcripts differ due to an alternative 5' splice site in the first exon of MAGOHB-204 . The alternate isoform lacks the first 46 amino acids compared to the principal isoform, which impacts key binding interfaces that may affect its function in the EJC.

How conserved is MAGOHB across species?

MAGOHB shows remarkable evolutionary conservation across vertebrates. The conservation pattern includes not only the principal isoform but also the alternate protein isoforms. Both the mouse ortholog Magohb and human MAGOHB generate two protein isoforms of comparable lengths (148 aa principal and 102 aa alternate isoforms), with similar splicing patterns . The high degree of conservation (generally above 70% identity, which is considered the threshold for functional preservation) suggests significant evolutionary pressure to maintain these isoforms, indicating their important biological roles.

What is the expression pattern of MAGOHB during development?

MAGOHB and its paralog MAGOH show distinct expression patterns during development, particularly in brain development. According to the Cortecon database referenced in the research, both genes show dynamic expression during cortex development . This developmental regulation is particularly significant as Magoh-haplo-insufficient mice demonstrate smaller brains due to defects in neuronal stem cell division, suggesting that proper dosage of these proteins is critical for normal neurogenesis and brain development .

What are the main biological functions of MAGOHB?

MAGOHB is involved in multiple biological processes:

• RNA Splicing: As a core EJC component, it plays a crucial role in splicing regulation and coordinating the correct order of intron excision .

• Neurogenesis and Brain Development: MAGOHB has significant roles in brain development, with alterations affecting neuronal differentiation .

• Cell Cycle Regulation: It influences cell division and cell cycle progression .

• Apoptosis: MAGOHB has been implicated in programmed cell death pathways .

• RNA Surveillance: It contributes to RNA quality control mechanisms .

These multiple functions make MAGOHB a critical factor in both normal cellular processes and disease states when its expression or function is dysregulated.

How does MAGOHB interact with the Exon Junction Complex?

MAGOHB, like MAGOH, forms a heterodimer with RBM8A, which together with eIF4A3 comprises the core of the Exon Junction Complex. This complex is deposited 24 bases upstream of exon-exon junctions during splicing . The EJC plays crucial roles in multiple post-splicing events including mRNA export, translation, and nonsense-mediated decay. Research indicates that exons with higher EJC occupancy are more sensitive to MAGOHB/MAGOH knockdown, suggesting that stronger EJC presence is required to prevent aberrant splicing events at these junctions .

What are the recommended approaches for analyzing MAGOHB isoform expression?

To analyze MAGOHB isoform expression, researchers can employ several complementary methods:

• RT-PCR: Using primers spanning the alternative splice junctions to distinguish between isoforms. This approach was used to verify the expression of alternate transcripts in HEK-293 cells .

• RNA-Seq: For genome-wide analysis of transcript variants and their relative abundance.

• Western Blotting: Using antibodies recognizing shared or unique epitopes of MAGOHB isoforms.

• Isoform-Specific Knockdown: Using siRNAs or antisense oligonucleotides targeting unique regions of specific isoforms.

When designing these experiments, researchers should consider the high sequence similarity between MAGOH and MAGOHB, which can complicate isoform-specific detection.

How should MAGOHB knockdown experiments be designed?

When designing MAGOHB knockdown experiments, researchers should consider:

• Targeting Strategy: Due to potential functional redundancy between MAGOH and MAGOHB, dual knockdown may be necessary to observe phenotypic effects, as demonstrated in the U251 and U343 glioblastoma cell models .

• Cell Type Selection: Different cell types may respond differently to MAGOHB depletion. For example, knockdown affects viability in glioma cells but not in normal astrocytes .

• Validation: Confirm knockdown efficiency at both mRNA and protein levels.

• Phenotypic Assays: Include analyses for cell viability, proliferation, apoptosis, and cell cycle distribution, which are all affected by MAGOHB depletion in cancer cells .

• Controls: Include appropriate controls, especially when studying both paralogs simultaneously.

What methods can detect aberrant splicing events following MAGOHB manipulation?

To detect aberrant splicing events following MAGOHB manipulation, researchers can use:

• RNA-Seq Analysis: To identify global changes in splicing patterns, particularly exon skipping events which increase following MAGOHB knockdown .

• Junction-Specific PCR: To validate specific aberrant splicing events identified in RNA-Seq data.

• EJC Occupancy Analysis: Correlating EJC binding sites with exons affected by MAGOHB knockdown to identify functional relationships .

• Splicing Reporter Assays: Using minigene constructs to study the effects of MAGOHB on specific splicing events in isolation.

Research shows that MAGOHB/MAGOH knockdown leads to increased exon-skipping events, particularly affecting genes involved in cell division, cell cycle, splicing, and translation .

What is the relationship between MAGOHB expression and cancer progression?

MAGOHB and MAGOH are aberrantly expressed in multiple tumor types and have been identified as potential oncogenic factors. Key findings include:

This suggests MAGOHB/MAGOH act as oncogenic factors, particularly in brain tumors.

How does MAGOHB contribute to glioblastoma pathogenesis?

MAGOHB contributes to glioblastoma (GBM) pathogenesis through several mechanisms:

• Splicing Regulation: MAGOHB helps safeguard the splicing of genes required for increased cell proliferation in GBM growth .

• Cell Cycle Control: It supports the expression of genes involved in cell division and cell cycle regulation .

• Gene Expression: MAGOHB ensures efficient splicing and translation of genes in high demand during rapid proliferation .

• Differential Requirement: While GBM cells require high MAGOHB/MAGOH expression, differentiated neuronal cells do not, suggesting a cancer-specific dependence .

These findings indicate that MAGOHB supports GBM growth by maintaining the expression of genes essential for rapid cell proliferation and division.

Can MAGOHB be targeted for cancer therapy?

Based on current research, MAGOHB represents a potential therapeutic target for cancer, particularly glioblastoma:

• Selective Requirement: Knockdown of MAGOHB/MAGOH affects viability of glioma cells but not normal astrocytes, suggesting a therapeutic window .

• Essential Function: MAGOHB is required for efficient cell division and cell cycle progression in cancer cells .

• Expression Pattern: Differentiated neuronal cells do not require increased MAGOHB/MAGOH expression, reducing potential off-target effects .

While no specific MAGOHB inhibitors have been reported in the provided research, the differential requirement between cancer and normal cells makes it a promising target for future therapeutic development. Researchers are advised to explore RNA interference approaches, small molecule inhibitors of protein-protein interactions, or antisense technologies to target MAGOHB in preclinical models.

How do the functions of MAGOHB and MAGOH paralogs differ?

Despite their high sequence similarity, MAGOHB and MAGOH may have distinct as well as overlapping functions:

• Evolutionary Conservation: Both paralogs are conserved across vertebrates, suggesting distinct selective pressures .

• Isoform Patterns: Both paralogs generate alternative protein isoforms that are also evolutionarily conserved, indicating functional significance .

• Compensatory Mechanisms: Research suggests some functional redundancy, as experimental approaches often target both paralogs simultaneously to observe phenotypic effects .

• Tissue-Specific Roles: Differences in expression patterns may indicate tissue-specific functions that require further investigation.

Researchers should consider designing experiments that can distinguish between the functions of these paralogs, potentially through paralog-specific knockdown or overexpression of specific isoforms.

What is the relationship between EJC occupancy and MAGOHB function?

Research reveals an important relationship between EJC occupancy and MAGOHB function:

• Splicing Regulation: Exons located upstream from those that were skipped in MAGOHB/MAGOH knockdown cells had a higher rate of EJC occupancy .

• Aberrant Splicing: This suggests that a stronger EJC presence is required to prevent aberrant splicing events at certain exon junctions .

• Exon Skipping: MAGOHB/MAGOH knockdown leads to increased exon-skipping events, particularly affecting multiple exons simultaneously .

These findings indicate that MAGOHB, as part of the EJC, plays a critical role in maintaining splicing fidelity, particularly at exon junctions with high EJC occupancy. This relationship provides insights into how MAGOHB dysfunction may lead to widespread splicing aberrations affecting critical cellular processes.

How should researchers approach studying the specific functions of MAGOHB isoforms?

Studying the specific functions of MAGOHB isoforms presents challenges due to sequence similarity between isoforms and paralogs. Researchers should consider:

• Isoform-Specific Expression: Developing systems for expressing individual isoforms in the absence of endogenous proteins, as suggested in the research: "the function of the alternate isoforms might need to be analysed in conditions where the principal isoform is absent" .

• Domain Analysis: Investigating the functional implications of missing amino acid residues in the alternate isoforms, which may affect protein-protein interactions or subcellular localization.

• Evolutionary Approach: Leveraging the conservation of isoforms across species to identify functionally important regions.

• Interaction Studies: Determining whether alternate isoforms have different binding partners or compete with principal isoforms for the same interactions.

• Regulatory Analysis: Exploring whether alternate isoforms regulate the levels of principal isoforms or have entirely different functions .

These approaches can help delineate the specific roles of MAGOHB isoforms in normal cellular processes and disease states.