MAGEB17

Key takeaways

MAGEB17 belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect MAGEB17 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of MAGEB17 from memory before moving on to harder problems.

Reference excerpt

Melanoma-associated antigen B17 (MAGEB17) is a protein which in humans is encoded by the MAGEB17 gene located on the X chromosome (Xp22.2). The protein has a molecular mass of approximately 37.4 kDa and an isoelectric point of approximately 9.25. MAGEB17 is classified as a cancer-testis antigen, with expression in normal adult tissues primarily restricted to germ cells and re-expression observed in a subset of human tumors.

Gene MAGEB17 is a protein-coding gene on chromosome X (Xp22.2), on the plus strand, spanning 3,984 bp across two exons. MAGEB17 is a member of the MAGEB gene family, in which the entire CDS is located within the last exon. MAGEB17 is classified as a cancer-testis antigen, with expression in normal adult tissues restricted to germ cells.

Transcripts MAGEB17 produces a canonical transcript (NM_001277307.2) of 1,434 nt. One splice variant exists (XM_047442355.1, 1,566 nt), differing from the canonical transcript in the 5' UTR.

Protein The MAGEB17 gene produces two isoforms, both 336 amino acids in length. The canonical protein, Melanoma-associated antigen B17 (NP_001264236.1), has a predicted molecular mass of ~37.4 kDa and a theoretical isoelectric point of ~9.25, indicating a basic protein at physiological pH. Melanoma-associated antigen B17 isoform X1 (XP_047298311.1) is also 336 aa, differing from the canonical transcript in the 5' UTR. Gene Ontology annotations associate MAGEB17 with the negative regulation of transcription by RNA polymerase II and with activity in the nucleus.

Structure The protein contains two conserved domains: an N-terminal MAGE domain (MAGE_N, residues 5–93) and a MAGE homology domain (MHD, residues 116–283). The MHD serves as a structural scaffold, a feature conserved across the MAGE protein family. Multiple sequence alignments indicate that a C-terminal core region flanks the MHD and is highly conserved across mammalian orthologs.

Gene level regulation

Expression MAGEB17 is non-ubiquitously expressed, with expression in normal adult tissues restricted to germ cells. Testis is the predominant site of expression, with all other normal adult tissues at near-zero levels. Expression is transiently detected in fetal heart tissue at 18 weeks gestational age. No substantial expression has been detected in any brain region in either fetal or adult tissue. In cancer, MAGEB17 is reactivated across a subset of tumor types including colon, rectal, and liver adenocarcinomas, and testicular germ cell tumors.

Promoter The MAGEB17 promoter contains binding sites for transcription factors associated with cancer-testis antigen reactivation and germ cell biology, including STAT3, SRY, Nanog, and CREM. Promoter sequence conservation is largely restricted to primates, consistent with the primate-specific distribution of the MAGE gene family.

Protein level regulation MAGEB17 contains several experimentally confirmed and predicted regulatory modifications. Threonine 131 (T131), located at the MHD boundary, has been experimentally identified as a phosphorylation site and is conserved across mammalian orthologs. Two predicted SUMOylation sites exist at K88 and K292. A predicted SPOP degron motif is present at residues 39–43. A predicted MAPK docking motif at residues 152–160 suggests potential regulation by mitogen-activated protein kinase signaling.

Subcellular localization MAGEB17 localizes primarily to the nucleus, consistent with two predicted nuclear localization signals at residues 7–12 and 126–145. A cytoplasmic pool has also been observed, potentially reflecting pre-import localization prior to nuclear transport.

Homology and evolution

Paralogs

MAGEB17 is a member of the MAGE protein family, which comprises over 50 paralogs in humans. MAGEB4 shares greater sequence identity with MAGEB17 than MAGEB1, suggesting a closer evolutionary relationship within the MAGE-B subfamily.

Orthologs

MAGEB17 orthologs are found exclusively in mammals, consistent with the mammal-specific expansion of the MAGE protein family. Sequence identity decreases with increasing evolutionary distance from humans.

Rate of divergence

MAGEB17 diverges more rapidly than both Cytochrome c and Complement factor I, suggesting relatively weak purifying selection on the protein sequence compared to these broadly expressed proteins.

Distant homologs The most distant detectable homolog is the Drosophila melanogaster MAGE protein, sharing 16.9% sequence identity with human MAGEB17, with conservation restricted to the MAGE homology domain.

Interacting proteins

STRING analysis identifies several predicted functional partners for MAGEB17, primarily on the basis of co-expression and text mining. No experimentally validated protein-protein interactions have been identified for MAGEB17 in BioGRID. A single genetic interaction with LDLR is recorded, though this is considered a likely artifact given the high-throughput nature of the screen.

Clinical significance MAGEB17 is classified as a cancer-testis antigen, with expression silenced in normal somatic tissues via DNA methylation and reactivated in a subset of tumors. RNA expression data indicate enrichment in colon, rectal, and liver adenocarcinomas, and testicular germ cell tumors. A stop-gain variant (V297*) has been identified, resulting in a truncated protein. By virtue of its tumor-specific expression, MAGEB17 represents a potential target for cancer immunotherapy. Because of its tumor-associated expression pattern, MAGEB17 has been proposed as a potential target for cancer immunotherapy.

References

Suggested reading Chomez P, et al. An Overview of the MAGE Gene Family with the Identification of All Human Members of the Family. Cancer Res. 2001.

Illustrations

Worked examples

Example 1 — a first encounter with MAGEB17

Start with the simplest possible case. Write down what MAGEB17 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to MAGEB17 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about MAGEB17 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of MAGEB17

In research: MAGEB17 appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses MAGEB17 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: MAGEB17 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Antigens, Genes on human chromosome X, Melanoma, so understanding it makes those chapters shorter.
In everyday life: Look for MAGEB17 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study MAGEB17 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what MAGEB17 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain MAGEB17 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is MAGEB17 in simple terms?

Melanoma-associated antigen B17 (MAGEB17) is a protein which in humans is encoded by the MAGEB17 gene located on the X chromosome (Xp22.2). The protein has a molecular mass of approximately 37.4 kDa and an isoelectric point of approximately 9.25.

Why does MAGEB17 matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study MAGEB17?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on MAGEB17.