Final answer:
The question discusses mRNA sequences that enable ribosome recruitment and initiate translation without needing all the usual initiation factors like eIF4E in eukaryotes. Internal ribosome entry sites (IRES) within mRNA allow translation initiation with a reduced set of factors by forming a structure that the ribosome can bind directly, bypassing the need for cap recognition.
Step-by-step explanation:
The question refers to the specific mRNA sequences that are capable of forming a secondary structure which then recruits the ribosome for the initiation of protein translation in eukaryotes. Unlike the prokaryotic system, which relies on the Shine-Dalgarno sequence, eukaryotic mRNA is typically translated by binding to a 7-methylguanosine cap at the 5' end. However, some mRNA sequences can form internal ribosome entry sites (IRES), which allow translation initiation to occur with fewer initiation factors and without the need for the cap-binding complex including eIF4E.
In the context of eukaryotic translation, the 40S ribosomal subunit scans the mRNA to locate the start codon (AUG) within the open reading frame (ORF). The initiation complex, including factors such as eukaryotic initiation factor-2 (eIF-2) bound to GTP and the initiator tRNA, aligns with the start codon, leading to the assembly of the full ribosome and the start of translation. A key feature in this process is the cap-binding complex, which normally includes eIF4E, but in the case of IRES-driven initiation, such factors are not required.