What is the Origin of (TAAAA)n Repeat?

This is a term from genetic biology and endocrinology, specifically defining a short tandem repeat element within a crucial regulatory gene. Its discovery provided a molecular explanation for some of the inherited variability observed in plasma SHBG concentrations among individuals. The concept is rooted in the study of how non-coding DNA sequences modulate protein synthesis.

What is the Mechanism of (TAAAA)n Repeat?

The precise number of TAAAA motifs acts as a rheostat, controlling the basal rate of SHBG gene transcription in the liver. A higher number of these repeats, such as alleles with more than eight, typically diminishes the promoter's strength and lowers SHBG protein synthesis. This reduction in circulating SHBG alters the ratio of free-to-bound sex steroids. This shift potentially increases the biological impact of androgens and estrogens on target tissues.

(TAAAA)n Repeat

Meaning

A non-coding, highly polymorphic region in the regulatory promoter sequence of the Sex Hormone-Binding Globulin (SHBG) gene. This genetic structure is characterized by a tandem arrangement of the adenine and thymine rich sequence TAAAA, with the total number of repeats influencing gene expression. It functions as a key determinant in an individual’s intrinsic capacity to produce the SHBG protein. This repeat length variation is a common genetic factor that contributes to hormonal diversity among populations.