该基因编码转录因子成对盒（PAX）家族的一个成员。这个基因家族的核心特征是一个新颖的，高度保守的DNA结合基序，即成对盒。成对盒转录因子是早期发育的重要调节因子，其基因表达的改变被认为有助于肿瘤的转化。该基因编码B细胞系特异性激活蛋白，在B细胞分化的早期而非晚期表达。它在中枢神经系统和睾丸的发育中也有表达，因此编码蛋白也可能在神经发育和精子发生中发挥作用。这个基因位于9p13，它参与了T（9；14）（p13；q32）易位，在浆细胞亚型的小淋巴细胞淋巴瘤和衍生大细胞淋巴瘤中复发。这种易位使得有效的IGH基因E-MU增强子与PAX5启动子非常接近，这表明该基因转录的放松调控有助于这些淋巴瘤的发病机制。选择性剪接导致编码不同亚型的多个转录变体。
This gene encodes a member of the paired box (PAX) family of transcription factors. The central feature of this gene family is a novel, highly conserved DNA-binding motif, known as the paired box. Paired box transcription factors are important regulators in early development, and alterations in the expression of their genes are thought to contribute to neoplastic transformation. This gene encodes the B-cell lineage specific activator protein that is expressed at early, but not late stages of B-cell differentiation. Its expression has also been detected in developing CNS and testis and so the encoded protein may also play a role in neural development and spermatogenesis. This gene is located at 9p13, which is involved in t(9;14)(p13;q32) translocations recurring in small lymphocytic lymphomas of the plasmacytoid subtype, and in derived large-cell lymphomas. This translocation brings the potent E-mu enhancer of the IgH gene into close proximity of the PAX5 promoter, suggesting that the deregulation of transcription of this gene contributes to the pathogenesis of these lymphomas. Alternative splicing results in multiple transcript variants encoding different isoforms.