Final answer:
The G quadraplex structure formed by poly-G sequences hinders protein synthesis by preventing ribosome binding to mRNA. Polysomes, which involve multiple ribosomes translating the same mRNA, are also affected, leading to a significant reduction in protein synthesis.
Step-by-step explanation:
The G quadraplex structure mentioned in the question refers to a four-stranded configuration formed by guanine-rich sequences of nucleotides, and in this context, specifically by poly-G sequences. This configuration can strongly impede protein synthesis as it prevents the ribosome from binding to the mRNA, which is necessary for translation. Translation itself is a multi-step process, involving initiation, elongation, and termination. During initiation, initiation factors are required to facilitate the assembly of the ribosomal subunits with the mRNA transcript. However, if a G quadraplex structure is present, these initiation factors may not be able to bind, leading to a failure in the formation of the initiation complex.
Furthermore, the presence of polysomes implies that multiple ribosomes are typically involved in translating a single mRNA molecule concurrently. In normal conditions, this allows for efficient and rapid protein production. However, if poly-G sequences form G quadraplexes, this can prevent not only a single ribosome but effectively all ribosomes in the polysome from initiating translation, leading to a significant reduction in protein synthesis. This could have important implications in cellular function and regulation.