The best-studied example of cap-independent translation initiation in eukaryotes uses the internal ribosome entry site (IRES). Unlike cap-dependent translation, cap-independent translation does not require a 5 cap to initiate scanning from the 5 end of the mRNA until the start codon. The ribosome can localize to the start site by direct binding, initiation factors, and/or ITAFs (IRES trans-acting factors) bypassing the need to scan the entire 5' UTR. This method of translation is important in conditions that require the translation of specific mRNAs during cellular stress, when overall translation is reduced. Examples include factors responding to apoptosis and stress-induced responses.