Ben-Chetrit E
Department of Internal Medicine, Hadassah University Hospital, Jerusalem, Israel.
Am J Reprod Immunol. 1992 Oct-Dec;28(3-4):256-8. doi: 10.1111/j.1600-0897.1992.tb00809.x.
The SSA/Ro and SSB/La antigens are polypeptides which serve as autoantigens in systemic lupus erythematosus and Sjogren's syndrome. The SSA/Ro contains two major isoforms of 60 kD and 52 kD. The former is the main native antigen while the latter is a major autoantigen in its denatured form. The SSB/La is a single phosphorylated protein of 48 kD. Recently a new protein of 46 kD, termed calregulin, was suggested as an additional component of the SSA/Ro antigens. However, extensive investigations failed to confirm its relation to the SSA/Ro system. Based on molecular techniques and cDNA cloning of these antigens, it was demonstrated that the 60 kD protein is capable of binding RNA and DNA molecules, suggesting a regulatory role in transcription for this antigen. The 52 kD polypeptide contains multiple zinc finger motifs and its sequence is homologous to the mouse rptl protein, which is a T-cell regulating peptide. The SSB/La is associated with precursors of 5S RNA and tRNA, implying that it has a role in the synthesis and maturation of RNA polymerase III transcripts. The 60 kD and 52 kD SSA/Ro components may be associated within the cell. The SSA/Ro and SSB/La may also be in complex in some points of the cell cycle.
SSA/Ro和SSB/La抗原是多肽，在系统性红斑狼疮和干燥综合征中作为自身抗原。SSA/Ro包含60kD和52kD两种主要的同工型。前者是主要的天然抗原，而后者是其变性形式的主要自身抗原。SSB/La是一种48kD的单一磷酸化蛋白。最近，一种名为钙调节蛋白的46kD新蛋白被认为是SSA/Ro抗原的一个额外成分。然而，广泛的研究未能证实它与SSA/Ro系统的关系。基于这些抗原的分子技术和cDNA克隆，证明60kD蛋白能够结合RNA和DNA分子，表明该抗原在转录中起调节作用。52kD多肽包含多个锌指基序，其序列与小鼠rptl蛋白同源，后者是一种T细胞调节肽。SSB/La与5S RNA和tRNA的前体相关，这意味着它在RNA聚合酶III转录本的合成和成熟中起作用。60kD和52kD的SSA/Ro成分可能在细胞内相互关联。SSA/Ro和SSB/La在细胞周期的某些阶段也可能形成复合物。
