Müller Jan Paul, Scholl Stephan, Kunick Conrad, Klempnauer Karl-Heinz
Institut für Biochemie, Westfälische-Wilhelms-Universität Münster, Wilhelm-Klemm-Str. 2, D-48149 Münster, Germany.
Institut für Chemische und Thermische Verfahrenstechnik, Technische Universität Braunschweig, Langer Kamp 7, D-38106 Braunschweig, Germany; Zentrum für Pharmaverfahrenstechnik, Technische Universität Braunschweig, Franz-Liszt-Straße 35a, D-38106 Braunschweig, Germany.
Biochim Biophys Acta Mol Cell Res. 2021 Jan;1868(1):118894. doi: 10.1016/j.bbamcr.2020.118894. Epub 2020 Oct 19.
HIPK2 is a highly conserved, constitutively active Ser/Thr protein kinase that is involved in a broad spectrum of biological processes. We have previously reported that the expression of HIPK2 is auto-regulated by a mechanism that depends on the activity of its kinase domain, leading to decreased expression of kinase-dead versus wild-type HIPK2. We have now explored this mechanism in more detail. Differential expression of wild-type and kinase-dead HIPK2 is dependent on sequences located in the C-terminal part of HIPK2, but is only observed when this part of HIPK2 is translated together with the defective kinase domain. On their own, both the defective kinase domain and the C-terminal amino acid sequences are expressed at normal levels and independently of kinase activity. Insertion of a 2A-ribosomal skipping sequence into the HIPK2 coding sequence revealed that the differential expression of wild-type and kinase-dead HIPK2 is caused by degradation of nascent kinase-dead HIPK2. Because HIPK2 is constitutively active and auto-activates its kinase domain already during its translation we speculate that the regulatory mechanism discovered here serves as a quality control mechanism that leads to degradation of nascent kinase molecules with defective kinase domains. Overall our work provides insight into a novel auto-regulatory mechanism of HIPK2 expression, thereby adding a new layer of control to the regulation of HIPK2.
HIPK2是一种高度保守的、组成型激活的丝氨酸/苏氨酸蛋白激酶，参与广泛的生物学过程。我们之前报道过，HIPK2的表达通过一种依赖其激酶结构域活性的机制进行自我调节，导致激酶失活型HIPK2与野生型HIPK2相比表达降低。我们现在更详细地探究了这一机制。野生型和激酶失活型HIPK2的差异表达取决于HIPK2 C末端部分的序列，但只有当HIPK2的这一部分与有缺陷的激酶结构域一起翻译时才会观察到。单独来看，有缺陷的激酶结构域和C末端氨基酸序列都以正常水平表达，且与激酶活性无关。在HIPK2编码序列中插入一个2A核糖体跳跃序列表明，野生型和激酶失活型HIPK2的差异表达是由新生的激酶失活型HIPK2的降解引起的。由于HIPK2是组成型激活的，并且在其翻译过程中就已经自我激活其激酶结构域，我们推测这里发现的调节机制作为一种质量控制机制，导致具有缺陷激酶结构域的新生激酶分子降解。总体而言，我们的工作深入了解了HIPK2表达的一种新型自我调节机制，从而为HIPK2的调节增加了新的控制层面。
